Method for preparing aromatic secondary amino compound

ABSTRACT

Disclosed are (1) a method for preparing an aromatic secondary amino compound which comprises reacting an N-cyclohexylideneamino compound in the presence of a hydrogen moving catalyst and a hydrogen acceptor by the use of a sulfur-free polar solvent and/or a cocatalyst, and (2) a method for preparing an aromatic secondary amino compound which comprises reacting cyclohexanone or a nucleus-substituted cyclohexanone, an amine and a nitro compound corresponding to the amine in a sulfur-free polar solvent in the presence of a hydrogen moving catalyst, a cocatalyst being added or not added. In a further aspect, a method is provided for the preparation of aminodiphenylamine by reacting phenylenediamine and cyclohexanone in the presence of a hydrogen transfer catalyst in a sulfur-free polar solvent while using nitroaniline as a hydrogen acceptor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/287,273, filed on Aug. 8, 1994, now abandoned, which is a divisionalof application Ser. No. 08/100,149 filed on Aug. 2, 1993, now U.S. Pat.No. 5,382,690.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an improved method for preparing anaromatic secondary amino compound. The present invention also relates toan improved method for the preparation of aminodiphenylamine.

The aromatic secondary amino compound obtained by the method of thepresent invention is an extremely important industrial chemical such asa raw material for rubber chemicals, dyes and the like.

(b) Description of the Prior Art

As methods for preparing an aromatic secondary amino compound, there areknown a method in which the reaction of toluidine is carried out in aliquid phase at 300° to 400° C. in the presence of a suitableself-condensation type reaction catalyst (BF₃, FeCl₂, a salt of anammonium halogenide, or a mineral acid), and a method in which cresol isreacted with toluidine at 330° to 340° C. under pressure in the presenceof triphenyl phosphate.

Other methods for preparing the aromatic secondary amino compound arealso known which comprise the dehydrogenation reaction of anN-cyclohexylideneamino compound. For example, there are a method forobtaining N-cyclohexylidene-N'-isopropylphenylenediamine at atemperature of 350° C. or less in the presence of a dehydrogenationcatalyst (British Patent No. 989257); a method in which reaction iscarried out in a gaseous phase, while oxygen or an oxygen-containing gasis fed at 300° to 450° C. in the presence of an oxidizing catalyst suchas silica or alumina (Japanese Patent Application Laid-open No.49924/1974); a method for obtaining 4-methyldiphenylamine by reaction at300° to 500° C. in the presence of a dehydrogenation catalyst selectedfrom the group consisting of nickel, platinum, palladium andcopper-chromium alloy (Japanese Patent Application Laid-open No.49925/1974); and a method for preparing an amino compound by the use ofa specific nickel/chromium catalyst (Japanese Patent Publication No.4623/1982).

Still other methods are already known in which a nitro compound is usedas a hydrogen acceptor in the presence of a hydrogen moving catalyst toproduce an amine in the system, and a nucleus-substituted cyclohexanoneis simultaneously reacted with the amine to prepare an aromaticsecondary amino compound. For example, there are a method for obtainingp-ethoxydiphenylamine by reacting p-nitrophenetole with a large excessof cyclohexanone in the presence of a palladium catalyst (British PatentNo. 975097); a method for obtaining 2,6-dimethyldiphenylamine byreacting 1/3 mol of 2,6-dimethylaniline, 2/3 mol of2,6-dimethylnitrobenzene, and cyclohexanone in the presence of apalladium catalyst, the amount of cyclohexanone being 10% in excess ofthe total of 2,6-dimethylaniline and 2,6-dimethylnitrobenzene (BritishPatent No. 989257); and a method for preparing a diphenylaminederivative by reacting 2 -(alkyl or alkoxy)-4-alkoxynitrobenzene,2-(alkyl or alkoxy)-4-alkoxyaniline and cyclohexanone in the presence ofa palladium catalyst (Japanese Patent Application Laid-open No.117214/1993).

However, these conventional methods have drawbacks of (1) severereaction conditions, (2) a low reaction rate, and (3) a low yield. Forthese reasons, they are not industrially satisfactory manufacturingmethods.

Known preparation processes of 4-aminodiphenyl-amine includerearrangement and reduction of N-nitroso-diphenylamine obtained bynitrosation of p-phenylenediamine (P.B. Reports 77764, 27-32) andcondensation of formanilide or acetanilide with a halonitrobenzene,followed by reduction of the nitro group [Journal of Organic Chemistry,42(10), 1786-90]. Known preparation processes of 2-aminodiphenylamineinclude rearrangement of an azo compound [Journal of Organic Chemistry,295(1), 91-7, 1985]. Further, known preparation processes of3-aminodiphenylamine include reduction of 3-nitrodiphenylamine. They arehowever hardly considered as industrially advantageous processes,because they require a complex reaction step, a large amount of aspecial reagent and/or solvent, and/or a precise purification step.

It is also known, as in the further aspect of the present invention, toprepare aminodiphenylamine by reacting cyclohexanone andphenylenediamine in the presence of a hydrogen transfer catalyst and ahydrogen receptor. Pursuant to this process, aminodiphenylamine has beenobtained by reacting cyclohexanone and phenylenediamine in the presenceof a palladium catalyst while using α-methylstyrene as a hydrogenreceptor (Japanese Patent Laid-Open No. 58648/1982). In this process,however, except for its use as a hydrogen receptor, α-methylstyrenecannot effectively be used for the reaction, in contrast with thehydrogen receptor in this further aspect of the present invention, andphenylenediamine as a raw material has to be supplied in its entiretyinto the reaction system in the form of phenylenediamine. The reactionhas to be conducted at elevated temperature and pressure. This processis therefore hardly considered to be satisfactory as an industrialprocess.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an industriallyimproved method for preparing an aromatic secondary amino compound froman N-cyclohexylidene amino compound or cyclohexanone (inclusive of anucleus-substituted compound), and according to this method, theabove-mentioned problems can be solved.

As a result of various investigations, it has been found that thearomatic secondary amino compound can be obtained under extremelymoderate conditions in a high yield by (1) using a sulfur-free polarsolvent and/or a cocatalyst at the time of the dehydrogenation reactionof an N-cyclohexylideneamino compound in the presence of a hydrogenmoving catalyst and a hydrogen acceptor, or (2) reacting cyclohexanoneor a nucleus-substituted cyclohexanone with an amine in a sulfur-freepolar solvent in the presence of a hydrogen moving catalyst by the useof a nitro compound corresponding to the amine as a hydrogen acceptor,or adding a specific cocatalyst to this system and then reacting thesame. In consequence, one aspect of the present invention has beenattained.

In accordance with a further object, it has been found that uponreaction of phenylenediamine and cyclohexanone in the presence of ahydrogen transfer catalyst in a sulfur-free polar solvent, use ofnitroaniline as a hydrogen receptor makes it possible to obtainaminodiphenylamine in a high yield under extremely mild conditions andfurther to use as a raw material phenylenediamine formed fromnitroaniline in the reaction system, leading to the present invention.

Therefore, in a further aspect of the present invention, there is thusprovided a method for the preparation of aminodiphenylamine, whichcomprises reacting phenylenediamine and cyclohexanone in the presence ofa hydrogen transfer catalyst in a sulfur-free polar solvent while usingnitroaniline as a hydrogen acceptor.

According to the method of the further aspect of the present invention,aminodiphenylamine can be obtained in a high yield under extremely mildconditions. Additionally, phenylenediamine formed from nitroaniline canbe used as a raw material in the reaction system and at the same time,any surplus portion of phenylenediamine can be reused together with thecatalyst.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first aspect of the present invention is directed to a method forpreparing an aromatic secondary amino compound represented by theformula (2) ##STR1## wherein each R is a hydrogen atom, alkyl group,alkoxy group, amino group, hydroxyl group or fluorine; n is an integerof from 0 to 5; and R' is an alkyl group, phenyl group, benzyl group,naphthyl group, furyl group, furfuryl group or cyclohexyl group, and R'may be substituted by an alkyl group, alkoxy group, phenyl group,phenoxy group, cyclohexyl group, amino group, substituted amino group,carboxyl group, hydroxyl group or fluorine which comprises the step ofsubjecting, to a dehydrogenation reaction, an N-cyclohexylideneaminocompound represented by the formula (1) ##STR2## wherein R, R' and n aredefined above in the presence of a hydrogen moving catalyst and ahydrogen acceptor, said method being characterized in that a sulfur-freepolar solvent is used at the time of the dehydrogenation reaction.

The N-cyclohexylideneamino compound which is used as a starting materialcan be easily synthesized from an amine (or its derivative having anamino group with a substituent) and cyclohexanone or its derivative inaccordance with a known process.

Examples of the alkyl group represented by R in the formula (1) includemethyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl,phenylmethyl, amino-methyl, hydroxymethyl and fluoromethyl, and aboveall, methyl and ethyl are preferable.

Examples of the alkoxy group include methoxy, ethoxy, butoxy, pentyloxy,hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, dodecyloxy,hexadecyloxy, aminomethoxy and fluoromethoxy, and above all, methyloxy,ethyloxy are preferable.

Examples of the amino group include amino, methylamino, ethylamino,propylamino, isopropylamino, butylamino, isobutylamino, tert-butylamino,pentylamino, dimethylamino, diethylamino, cyclohexylamino andacetylamino.

Examples of the alkyl group represented by R' in the formula (1) includemethyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl,aminomethyl, aminoethyl, aminopropyl, 2-aminopropyl, 3-aminopropyl,aminobutyl and hydoxyethyl.

Examples of the phenyl group include phenyl, o-methylphenyl,m-methylphenyl, p-methylphenyl, p-ethyl-phenyl, p-propylphenyl,p-isopropylphenyl, p-butylphenyl, p-tert-butylphenyl, p-pentylphenyl,p-hexylphenyl, p-heptylphenyl, p-octylphenyl, p-nonylphenyl,p-decyl-phenyl, p-dodecylphenyl, p-hexadecylphenyl, 3,4-dimethylphenyl,2,3-dimethylphenyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl,p-methoxyphenyl, p-ethoxyphenyl, p-butoxyphenyl, p-pentyloxyphenyl,p-hexyloxyphenyl, p-heptyloxyphenyl, p-octyloxyphenyl, p-nonyloxyphenyl,p-phenyloxyphenyl, p-trioxyphenyl, p-acetylphenyl, p-benzoylphenyl,p-aminophenyl, m-aminophenyl, p-methylaminophenyl, p-ethylaminophenyl,p-butylaminophenyl, p-tert-butyl-aminophenyl, p-octylaminophenyl,p-dodecylaminophenyl, p-cyclohexylphenyl, p-methylcyclohexylphenyl,p-ethyl-cyclohexylphenyl, p-propylcyclohexylphenyl, p-hydroxy-phenyl,p-carboxyphenyl and p-fluorophenyl, and phenyl and p-methylphenyl arepreferable.

Examples of the benzyl group include benzyl, o-methylbenzyl,m-methylbenzyl, p-methylbenzyl, p-ethylbenzyl, p-propylbenzyl,p-isopropylbenzyl, p-butylbenzyl, p-tert-butylbenzyl, p-pentylbenzyl,p-hexylbenzyl, p-heptylbenzyl, p-octylbenzyl, p-nonylbenzyl,p-decylbenzyl, p-dodecylbenzyl, p-hexadecylbenzyl, p-acetylbenzyl,3,4-dimethylbenzyl, 2,3-dimethylbenzyl, 2,6-dimethylbenzyl,2,4,6-trimethylbenzyl, p-methoxybenzyl, p-ethoxybenzyl, p-butoxybenzyl,p-pentyloxybenzyl, p-hexyloxybenzyl, p-heptyloxybenzyl,p-octyloxybenzyl, p-nonyloxybenzyl, p-phenyloxybenzyl, p-tolyloxybenzyl,p-benzoylbenzyl, p-methylaminobenzyl, p-ethylaminobenzyl,p-butylaminobenzyl, p-tert-butylaminobenzyl, p-octylaminobenzyl,p-dodecylaminobenzyl, p-cyclohexylbenzyl, p-methylcyclohexylbenzyl,p-ethylcyclohexylbenzyl, p-propylcyclohexylbenzyl, p-hydroxybenzyl,p-carboxybenzyl and p-fluorobenzyl.

Examples of the cyclohexyl group include cyclohexyl, o-methylcyclohexyl,m-methylcyclohexyl, p-methylcyclohexyl, p-ethylcyclohexyl,p-propylcyclohexyl, p-isopropylcyclohexyl, p-butylcyclohexyl,p-tert-butylcyclohexyl, p-pentylcyclohexyl, p-hexylcyclohexyl,p-heptylcyclohexyl, p-octylcyclohexyl, p-nonylcyclohexyl,p-decylcyclohexyl, p-dodecylcyclohexyl, p-hexadecylcyclohexyl,p-acetylcyclohexyl, 3,4-dimethylcyclohexyl, 2,3-dimethylcyclohexyl,2,6-dimethylcyclohexyl, 2,4,6-trimethylcyclohexyl, p-methoxycyclohexyl,p-ethoxycyclohexyl, p-butoxycyclohexyl, p-pentyloxycyclohexyl,p-hexyloxycyclohexyl, p-heptyloxycyclohexyl, p-octyloxycyclohexyl andp-nonyloxycyclohexyl.

The preferred compounds of formula (1) are as follows:

1. N-(cyclohexylidene)methylamine

2. N-(4-methylcyclohexylidene)methylamine

3. N-(4-methyloxycyclohexylidene)methylamine

4. N-(cyclohexylidene)aniline

5. N-(2-methylcyclohexylidene)aniline

6. N-(3-methylcyclohexylidene)aniline

7. N-(4-methylcyclohexylidene)aniline

8. N-(4-ethylcyclohexylidene)aniline

9. N-(2,6-dimethylcyclohexylidene)aniline

10. N-(4-methyloxycyclohexylidene)aniline

11. N-(4-fluorocyclohexylidene)aniline

12. N-(4-hydroxycyclohexylidene)aniline

13. N-(cyclohexylidene)-2-methylaniline

14. N-(2-methylcyclohexylidene)-2-methylaniline

15. N-(3-methylcyclohexylidene)-2-methylaniline

16. N-(4-methylcyclohexylidene)-2-methylaniline

17. N-(4-ethylcyclohexylidene)-2-methylaniline

18. N-(2,6-dimethylcyclohexylidene)-2-methylaniline

19. N-(4-methyloxycyclohexylidene)-2-methylaniline

20. N-(4-fluorocyclohexylidene)-2-methylaniline

21. N-(4-hydroxycyclohexylidene)-2-methylaniline

22. N-(cyclohexylidene)-3-methylaniline

23. N-(2-methylcyclohexylidene)-3-methylaniline

24. N-(3-methylcyclohexylidene)-3-methylaniline

25. N-(4-methylcyclohexylidene)-3-methylaniline

26. N-(4-ethylcyclohexylidene)-3-methylaniline

27. N-(2,6-dimethylcyclohexylidene)-3-methylaniline

28. N-(4-methyloxycyclohexylidene)-3-methylaniline

29. N-(4-fluorocyclohexylidene)-3-methylaniline

30. N-(4-hydroxycyclohexylidene)-3-methylaniline

31. N-(cyclohexylidene)-4-methylaniline

32. N-(2-methylcyclohexylidene)-4-methylaniline

33. N-(3-methylcyclohexylidene)-4-methylaniline

34. N-(4-methylcyclohexylidene)-4-methylaniline

35. N-(4-ethylcyclohexylidene)-4-methylaniline

36. N-(2,6-dimethylcyclohexylidene)-4-methylaniline

37. N-(4-methyloxycyclohexylidene)-4-methylaniline

38. N-(4-fluorocyclohexylidene)-4-methylaniline

39. N-(4-hydroxycyclohexylidene)-2-methylaniline

40. N-(cyclohexylidene)-2,4-dimethylaniline

41. N-(2-methylcyclohexylidene)-2,4-dimethylaniline

42. N-(3-methylcyclohexylidene)-2,4-dimethylaniline

43. N-(4-methylcyclohexylidene)-2,4-dimethylaniline

44. N-(4-ethylcyclohexylidene)-2,4-dimethylaniline

45. N-(2,6-dimethylcyclohexylidene)-2,4-(dimethylaniline)

46. N-(4-methyloxycyclohexylidene)-2,4-(dimethylaniline)

47. N-(4-fluorocyclohexylidene)-2,4-dimethylaniline

48. N-(4-hdyroxycyclohexylidene)-2,4-dimethylaniline

49. N-(cyclohexylidene)-4-methoxyaniline

50. N-(2-methylcyclohexylidene)-4-methoxyaniline

51. N-(3-methylcyclohexylidene)-4-methoxyaniline

52. N-(4-methylcyclohexylidene)-4-methoxyaniline

53. N-(4-ethylcyclohexylidene)-4-methoxyaniline

54. N-(2,6-dimethylcyclohexylidene)-4-methoxyaniline

55. N-(4-methyloxycyclohexylidene)-4-methoxyaniline

56. N-(4-fluorocyclohexylidene)-4-methoxyaniline

57. N-(4-hydroxycyclohexylidene)-4-methoxyaniline

58. N-(cyclohexylidene)-4-hydroxyaniline

59. N-(2-methylcyclohexylidene)-4-hydroxyaniline

60. N-(3-methylcyclohexylidene)-4-hydroxyaniline

61. N-(4-methylcyclohexylidene)-4-hydroxyaniline

62. N-(4-ethylcyclohexylidene)-4-hydroxyaniline

63. N-(2,6-dimethylcyclohexylidene)-4-hydroxyaniline

64. N-(4-methyloxycyclohexylidene)-4-hydroxyaniline

65. N-(4-fluorocyclohexylidene)-4-hydroxyaniline

66. N-(4-hydroxycyclohexylidene)-4-hydroxyaniline

67. N-(cyclohexylidene)benzylamine

68. N-(2-methylcyclohexylidene)benzylamine

69. N-(3-methylcyclohexylidene)benzylamine

70. N-(4-methylcyclohexylidene)benzylamine

71. N-(4-ethylcyclohexylidene)benzylamine

72. N-(2,6-dimethylcyclohexylidene)benzylamine

73. N-(4-methyloxycyclohexylidene)benzylamine

74. N-(4-fluorocyclohexyliene)benzylamine

75. N-(4-hydroxycyclohexylidene)benzylamine

76. N-(cyclohexylidene)cyclohexyl

77. N-(2-methylcyclohexylidene)cyclohexyl

78. N-(3-methylcyclohexylidene)cyclohexyl

79. N-(4-methylcyclohexylidene)cyclohexyl

80. N-(4-ethylcyclohexylidene)cyclohexyl

81. N-(2,6-dimethylcyclohexylidene)cyclohexyl

82. N-(4-methyloxycyclohexylidene)cyclohexyl

83. N-(4-fluorocyclohexylidene)cyclohexyl

84. N-(4-hydroxycyclohexylidene)cyclohexyl

85. N-(cyclohexylidene)-4-fluoroaniline

86. N-(2-methylcyclohexylidene)-4-fluoroaniline

87. N-(3-methylcyclohexylidene)-4-fluoroaniline

88. N-(4-methylcyclohexylidene)-4-fluoroaniline

89. N-(4-ethylcyclohexylidene)-4-fluroaniline

90. N-(2,6-dimethylcyclohexylidene)-4-fluroaniline

91. N-(4-methyloxycyclohexylidene)-4-fluoroaniline

92. N-(4-fluorocyclohexylidene)-4-fluoroaniline

93. N-(4-hydroxycyclohexylidene)-4-fluoroaniline

94. N-(2-methylcyclohexylidene)methylamine

95. N-(3-methylcyclohexylidene)methylamine

96. N-(4-ethylcyclohexylidene)methylamine

97. N-(2,6-dimethylcylohexylidene)methylamine

98. N-(4-methyloxycyclohexylidene)methylamine

99. N-(4-fluorocyclohexylidene)methylamine

100. N-(4-hydroxycyclohexylidene)methylamine

101. N-(cyclohexylidene)-4-phenoxyaniline

102. N-(2-methylcyclohexylidene)-4-phenoxyaniline

103. N-(3-methylcyclohexylidene)-4-phenoxyaniline

104. N-(4-methylcyclohexlidene)-4-phenoxyaniline

105. N-(4-ethylcyclohexylidene)-4-phenoxyaniline

106. N-(2,6-dimethylcyclohexylidene)-4-phenoxyaniline

107. N-(4-methyloxycyclohexylidene)-4-phenoxyaniline

108. N-(4-fluorocyclohexylidene)-4-phenoxyaniline

109. N-(4-hydroxycyclohexylidene)-4-phenoxyaniline

110. N-(cyclohexylidene)-4-fluoroaniline

111. N-(2-methylcyclohexylidene)-4-fluoroaniline

112. N-(3-methylcyclohexylidene)-4-fluroaniline

113. N-(4-methylcyclohexylidene)-4-fluroaniline

114. N-(4-ethylcyclohexylidene)-4-fluoroaniline

115. N-(2,6-dimethylcyclohexylidene)-4-fluoroaniline

116. N-(4-methyloxycyclohexylidene)-4-fluoroaniline

117. N-(4-fluorocyclohexylidene)-4-fluoroaniline

118. N-(4-hydroxycyclohexylidene)-4-fluoroaniline

119. N-(cyclohexylidene)-2-aminoaniline

120. N-(cyclohexylidene)-3-aminoaniline

121. N-(cyclohexylidene)-4-aminoaniline

As the hydrogen moving catalyst, there can be used any known hydrogenmoving catalyst. Typical examples of the hydrogen moving catalystinclude Raney nickel, reduced nickel and nickel supporting catalystsobtained by supporting nickel on various carriers such as diatomaceousearth, alumina, pumice, silica gel and acidic terra abla; cobaltcatalysts such as Raney cobalt, reduced cobalt, cobalt andcobalt-carrier catalysts; copper catalysts such as Raney copper, reducedcopper and copper-carrier catalysts; palladium catalysts such aspalladium black, palladium oxide, colloidal palladium, palladium-carbon,palladium-barium sulfate and palladium-barium carbonate; platinumcatalysts such as platinum black, colloidal platinum, platinum sponge,platinum oxide, platinum sulfide, platinum-carbon and platinum-carriercatalysts; rhodium catalysts such as colloidal rhodium, rhodium-carbonand rhodium oxide; a platinum group catalyst such as a rutheniumcatalyst; rhenium catalysts such as dirhenium heptaoxide andrhenium-carbon; a copper chromium oxide catalyst; a molybdenum oxidecatalyst; a vanadium oxide catalyst; and a tungsten oxide catalyst.Among these catalysts, the palladium catalyst is preferable. Inparticular, the palladium-carrier catalyst is preferable. Above all, thepalladium-carbon and palladium-alumina are most preferable.

The amount of the hydrogen moving catalyst is usually in the range offrom 0.001 to 1.0 gram atom, preferably from 0.002 to 0.2 gram atom interms of a metallic atom per gram molecule of the N-cyclohexylideneaminocompound.

In the first aspect of the present invention, any of various reducingmaterials is used as a hydrogen acceptor. Examples of the hydrogenacceptor include olefin compounds such as 1-octene, allylbenzene andcrotonic acid; nitro compounds such as 2,6-dimethylnitrobenzene,p-amylnitrobenzene, p-hexylnitrobenzene, p-octylnitrobenzene,p-sec-octylnitrobenzene, p-tert-octylnitrobenzene, p-nonylnitrobenzene,p-decylnitrobenzene, p-ethoxynitrobenzene, o-ethoxynitrobenzene,2,6-dimethyl-4-aminonitrobenzene, nitrobenzene, p-dinitrobenzene,m-dinitrobenzene, 4-nitrodiphenyl, p-phenoxynitrobenzene,p-cyclohexylnitrobenzene, p-benzylnitrobenzene, nitromethane,2-nitropropane, 1-nitronaphthalene, 2-, 3- and 4-nitrotoluenes,4-nitroanisole, p-propylnitrobenzene, m-ethylnitrobenzene,4-nitrobenzonitrile, p-nitroacetoanilide, 4-nitrobenzoic acid andnitrocyclohexane; phenols, for example, alkylphenols such as phenol,methylphenol, ethylphenol, isopropylphenol, butylphenol,2,4-dimethylphenol, 2,4,6-trimethylphenol and2,6-di-tert-butyl-4-methylphenol as well as alkoxyphenols such as3-methoxyphenol and 4-methoxyphenol.

However, in the case that the phenol is selected, it must be used inlarge quantities and there is the tendency that the amounts ofby-products increase. It is particularly preferable to use nitrobenzenein the above-mentioned nitro compounds as the hydrogen acceptor, becausenitrobenzene can be utilized as the material ofN-cyclohexylideneaniline.

The amount of the hydrogen acceptor to be used depends upon its kind,but it is 5 equivalents of the hydrogen acceptor to theN-cyclohexylideneamino compound. Particularly in the case of the olefinor the nitro compound, the amount of the hydrogen acceptor is anequivalent or 50% excess of the N-cyclohexylideneamino compound. Whenthe hydrogen acceptor is short, the by-product of N-cyclohexylaminetends to increase. As the hydrogen acceptor, the olefin or the nitrocompound is preferable from the viewpoint of the volume efficiency of areactor.

Examples of the sulfur-free polar solvent to be used includeN,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, methylisobutyl ketone, tetrahydrofuran, dioxane, 1,3-dimethylimidazolizinone,glymes such as ethylene glycol dimethyl ether and diethylene glycoldimethyl ether, methyl salicylate, phenol and phenols, for example,alkylphenols such as methylphenol and 2,4,6-trimethylphenol as well asalkoxyphenols such as 3-methoxyphenol and 4-methoxyphenol. If necessary,they may be used in combinations of two or more thereof. Dimethylsulfoxide and sulfolane are similarly within the category of the polarsolvents, but they are not used because they contain sulfur which ispoisonous to the dehydrogenation catalyst.

The amount of the sulfur-free polar solvent to be used is preferably0.05-3.0 times by weight, more preferably 0.15-1.5 times by weight asmuch as that of the N-cyclohexylideneamino compound.

In placing the starting materials in a reactor, it is a preferablemanner that the solvent and the catalyst are previously placed in thereactor and mixed, and the N-cyclohexylideneamino compound and thehydrogen acceptor are then simultaneously dropped into the reactor tocarry out the above-mentioned reaction. Needless to say, alternatively,the N-cyclohexylideneamino compound and the hydrogen acceptor may befirst mixed and then added into the reaction.

In the above-mentioned dehydrogenation reaction of theN-cyclohexylideneamino compound in the presence of the hydrogen movingcatalyst and the hydrogen acceptor, an alkali metal compound and/or analkaline earth metal compound can be added as a cocatalyst to thereaction system irrespective of the presence of the sulfur-free polarsolvent. This is also one embodiment of the first aspect of the presentinvention.

Usable examples of the alkali metal compound and/or the alkaline earthmetal compound which can be added as the cocatalyst are hydroxides,carbonates, bicarbonates and the like of alkali metals and alkalineearth metals. Typical examples of these compounds include lithiumhydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide,magnesium hydroxide, sodium carbonate, potassium carbonate and sodiumhydrogen carbonate. Above all, sodium hydroxide and potassium hydroxideare preferable. These cocatalysts may be used singly or in combinationof two or more thereof. The cocatalyst does not have to be added to thereaction system separately from the above-mentioned dehydrogenationcatalyst. For example, after a noble metal supporting catalyst has beenprepared, a salt, a hydroxide or the like of an alkali metal and/or analkaline earth metal may be additionally supported as the alkali metalcomponent and/or the alkaline earth metal component on the noble metalsupporting catalyst, and the thus formed catalyst may be used.

The amount of the cocatalyst is preferably in the range of from 2 to 30%by weight, more preferably from 5 to 20% by weight, in terms of thealkali metal and/or the alkaline earth metal, based on the weight of thecatalyst metal. If the amount of the cocatalyst is in excess of thisrange, a reaction rate tends to deteriorate, and conversely if it isless than the range, the yield is low.

It is advantageous that the reaction is carried out under the removal ofwater, and thus a technique is suitable in which water is removed fromthe reaction mixture while azeotropic distillation is done by the use ofa solvent such as benzene, toluene or xylene.

The temperature of the reaction is usually in the range of from 120° to250° C., preferably from 140° to 200° C.

The mixture obtained by the above-mentioned method is treated in anordinary manner such as distillation, crystallization or extraction. Forexample, the solution in which the reaction has already been brought toan end is filtered to separate the catalyst therefrom. The thusrecovered catalyst can be reused. The resultant filtrate is concentratedto recover the solvent. The produced aromatic secondary amino compoundin the reactor can be directly used without any treatment, but ifnecessary, it may be purified by distillation, crystallization or thelike.

The second aspect of the present invention is directed to a method forpreparing an aromatic secondary amino compound represented by theformula (2) ##STR3## wherein each R is a hydrogen atom, alkyl group,alkoxy group, amino group, hydroxyl group or fluorine; R' is an alkylgroup, phenyl group, benzyl group, naphthyl group, furyl group, furfurylgroup or cyclohexyl group, and R' may be substituted by an alkyl group,alkoxy group, phenyl group, phenoxy group, cyclohexyl group, aminogroup, substituted amino group, carboxyl group, hydroxyl group orfluorine; and n is an integer of from 0 to 5 which comprises the step ofreacting cyclohexanone or a nucleus-substituted cyclohexanonerepresented by the formula (3) ##STR4## wherein R is defined above, anamine represented by the formula (4)

    R'--NH.sub.2                                               ( 4)

wherein R' is defined above, and a nitro compound corresponding to theamine and represented by the formula (5)

    R'--NO.sub.2                                               ( 5)

wherein R' is defined above as a hydrogen acceptor in a sulfur-freepolar solvent in the presence of a hydrogen moving catalyst.

That is, the second aspect of the present invention is directed to amethod for preparing an aromatic secondary amino compound which ischaracterized by comprising the step of reacting cyclohexanone or anucleus-substituted cyclohexanone, an amine and a nitro compound as ahydrogen acceptor corresponding to the amine in a sulfur-free polarsolvent in the presence of a hydrogen moving catalyst.

Examples of the alkyl group represented by R' in the formulae (4) and(5) include methyl, ethyl, propyl, isopropyl, butyl, isobutyl,tert-butyl, aminomethyl, aminoethyl, aminopropyl, 2-aminopropyl,3-aminopropyl, aminobutyl and hydoxyethyl.

Examples of the phenyl group include phenyl, o-methylphenyl,m-methylphenyl, p-methylphenyl, p-ethyl-phenyl, p-propylphenyl,p-isopropylphenyl, p-butylphenyl, p-tert-butylphenyl, p-pentylphenyl,p-hexylphenyl, p-heptylphenyl, p-octylphenyl, p-nonylphenyl,p-decylphenyl, p-dodecylphenyl, p-hexadecylphenyl, 3,4-dimethylphenyl,2,3-dimethylphenyl, 2,6-dimethylphenyl, 2,4,6-trimethyl-phenyl,p-methoxyphenyl, p-ethoxyphenyl, p-butoxyphenyl, p-pentyloxyphenyl,p-hexyloxyphenyl, p-heptyloxyphenyl, p-octyloxyphenyl, p-nonyloxyphenyl,p-phenyloxyphenyl, p-trioxyphenyl, p-acetylphenyl, p-benzoylphenyl,o-aminophenyl, m-aminophenyl, p-aminophenyl, p-methylaminophenyl,p-ethylaminophenyl, p-butylaminophenyl, p-tert-butylaminophenyl,p-octylaminophenyl, p-dodecylaminophenyl, p-cyclohexylphenyl,p-methylcyclohexylphenyl, p-ethylcyclohexylphenyl,p-propylcyclohexylphenyl, p-hydroxyphenyl, p-carboxyphenyl andp-fluorophenyl, and phenyl and p-methylphenyl are preferable.

Examples of the benzyl group include benzyl, o-methylbenzyl,m-methylbenzyl, p-methylbenzyl, p-ethylbenzyl, p-propylbenzyl,p-isopropylbenzyl, p-butylbenzyl, p-tert-butylbenzyl, p-pentylbenzyl,p-hexylbenzyl, p-heptylbenzyl, p-octylbenzyl, p-nonylbenzyl,p-decylbenzyl, p-dodecylbenzyl, p-hexadecylbenzyl, p-acetylbenzyl,3,4-dimethylbenzyl, 2,3-dimethylbenzyl, 2,6-dimethylbenzyl,2,4,6-trimethylbenzyl, p-methoxybenzyl, p-ethoxybenzyl, p-butoxybenzyl,p-pentyloxybenzyl, p-hexyloxybenzyl, p-heptyloxybenzyl,p-octyloxybenzyl, p-nonyloxybenzyl, p-phenyloxybenzyl, p-tolyloxybenzyl,p-benzoylbenzyl, p-methylaminobenzyl, p-ethylaminobenzyl,p-butylamino-benzyl, p-tert-butylaminobenzyl, p-octylaminobenzyl,p-dodecylaminobenzyl, p-cyclohexylbenzyl, p-methylcyclo-hexylbenzyl,p-ethylcyclohexylbenzyl, p-propylcyclohexyl-benzyl, p-hydroxybenzyl,p-carboxybenzyl and p-fluorobenzyl.

Examples of the cyclohexyl group include cyclohexyl, o-methylcyclohexyl,m-methylcyclohexyl, p-methylcyclohexyl, p-ethylcyclohexyl,p-propylcyclohexyl, p-isopropylcyclohexyl, p-butylcyclohexyl,p-tert-butylcyclohexyl, p-pentylcyclohexyl, p-hexylcyclohexyl,p-heptylcyclohexyl, p-octylcyclohexyl, p-nonylcyclohexyl,p-decylcyclohexyl, p-dodecylcyclohexyl, p-hexadecylcyclohexyl,p-acetylcyclohexyl, 3,4-dimethylcyclohexyl, 2,3-dimethylcyclohexyl,2,6-dimethylcyclohexyl, 2,4,6-trimethylcyclohexyl, p-methoxycyclohexyl,p-ethoxycyclohexyl, p-butoxycyclohexyl, p-pentyloxycyclohexyl,p-hexyloxycyclohexyl, p-heptyloxycyclohexyl, p-octyloxycyclohexyl andp-nonyloxycyclohexyl.

The preferred compounds of formula (3) are as follows:

1. cyclohexanone

2. 2-methylcyclohexanone

3. 3-methylcyclohexanone

4. 4-methylcyclohexanone

5. 4-ethylcyclohexanone

6. 4-octylcyclohexanone

7. 2,6-dimethylcyclohexanone

8. 2,4-dimethylcyclohexanone

9. 4-phenylcyclohexanone

10. 4-phenylmethylcyclohexanone

11. 4-phenyloxycyclohexanone

12. 4-methyloxycyclohexanone

13. 4-nonyloxycyclohexanone

14. 4-methylaminocyclohexanone

15. 4-dimethylaminocyclohexanone

16. 4-acetylaminocyclohexanone

17. 4-fluorocyclohexanone

18. 4-hydroxycyclohexanone

The preferred compounds of formula (4) are as follows:

1. methylamine

2. ethylamine

3. aniline

4. 2-methylaniline

5. 3-methylaniline

6. 4-methylaniline

7. 4-ethylaniline

8. 4-nonylaniline

9. 2,6-dimethylaniline

10. 2,4-dimethylaniline

11. 2,4,6-trimethylaniline

12. 4-methoxyaniline

13. 2-methyl-4-methoxyaniline

14. 4-acetylaniline

15. 4-aminoacetoanilide

16. 4-methylaminoaniline

17. 4-cyclohexylaniline

18. 4-hydroxyaniline

19. 4-carboxyaniline

20. benzylamine

21. 4-methylbenzylamine

22. 4-octylbenzylamine

23. 2,4-dimethylbenzylamine

24. 4-methoxybenzylanline

25. cyclohexylamine

26. 4-methylcyclohexylamine

27. 4-methyloxycycloamine

28. 2-naphthylamine

29. furfurylamine

30. 4-fluoroaniline

31. 4-aminodiphenylether

32. orthophenylenediamine

33. metaphenylenediamine

34. paraphenylenediamine

The preferred compounds of formula (5) are as follows:

1. nitromethane

2. nitroethane

3. nitrobenzene

4. 2-nitrotoluene

5. 3-nitrotoluene

6. 4-nitrotoluene

7. 4-ethylnitrobenzene

8. 4-nonylnitrobenzene

9. 2,6-dimethylnitrobenzene

10. 2,4-dimethylnitrobenzene

11. 2,4,6-trimethylnitrobezene

12. 4-methyoxynitrobenzene

13. 2-methyl-4-methoxynitrobenzene

14. 4-acetylnitrobezene

15. 4-nitroacetoanilide

16. 4-methylaminonitrobenzene

17. 4-cyclohexylnitrobenzene

18. 4-hydroxynitrobenzene

19. 4-carboxynitrobenzene

20. nitrobenzyl

21. 4-methylnitrobenzyl

22. 4-octylnitrobenzyl

23. 2,4-dimethylnitrobenzyl

24. 4-methoxynitrobenzyl

25. nitrocyclohexanone

26. 4-methylnitrocyclohexanone

27. 4-methoxynitrocyclohexanone

28. 2-nitronaphthalene

29. nitrofurfuryl

30. 4-fluoronitrobenzene

31. 4-nitrodiphenylether

32. orthonitroaniline

33. metanitroaniline

34. paranitroaniline

In the present invention, a molar ratio of the cyclohexanone or thenucleus-substituted cyclohexanone represented by the formula (3):theamine represented by the formula (4):the nitro compound represented bythe formula (5) is usually 3:1:2, and this ratio can be suitably alteredon the basis of the given values. The nitro compound behaves as thehydrogen acceptor to produce the amine in the reaction system, and thisamine causes a condensation reaction with the cyclohexanone or thenucleus-substituted cyclohexanone which is another starting material, toproduce a Schiff base. Afterward, the Schiff base is subjected todehydrogenation, thereby producing an aromatic secondary amino compound.In the dehydrogenation of the Schiff base, hydrogen is generated, and2/3 mol of the nitro compound per mol of the Schiff base can beconverted into the amine by the thus generated hydrogen.

Therefore, in order to completely effectively utilize the hydrogengenerated in the system, it is necessary to react the cyclohexanone orthe nucleus-substituted cyclohexanone and the nitro compound in a molarratio of 3:2. In this case, however, the excessive amount of thecyclohexanone or the nucleus-substituted cyclohexanone further reactswith the aromatic secondary amino compound produced in the system, sothat an aromatic tertiary amino compound tends to be produced as aby-product. Conversely, if the amount of the nitro compound isexcessive, the reaction rate tends to deteriorate inconveniently. Forthe purpose of avoiding these drawbacks, it is preferable that a molarratio of the cyclohexanone or the nucleus-substituted cyclohexanone:theamine compound:the nitro compound is 3:1:2, and more preferably, a molarratio of the sum of the nitro compound and the amine compound to thecyclohexanone or the nucleus-substituted cyclohexanone is in the rangeof from 0.9 to 1.2.

As the hydrogen moving catalyst which can be used in the method of thepresent invention, there can be used any known hydrogen moving catalyst.Typical examples of the hydrogen moving catalyst include Raney nickel,reduced nickel and nickel supporting catalysts obtained by supportingnickel on various carriers such as diatomaceous earth, alumina, pumice,silica gel and acidic terra abla; cobalt catalysts such as Raney cobalt,reduced cobalt, cobalt and cobalt-carrier catalysts; copper catalystssuch as Raney copper, reduced copper and copper-carrier catalysts;palladium catalysts such as palladium black, palladium oxide, colloidalpalladium, palladium-carbon, palladium-barium sulfate andpalladium-barium carbonate; platinum catalysts such as platinum black,colloidal platinum, platinum sponge, platinum oxide, platinum sulfide,and platinum-carrier catalysts such as platinum-carbon; rhodiumcatalysts such as colloidal rhodium, rhodium-carbon and rhodium oxide; aplatinum group catalyst such as a ruthenium catalyst; rhenium catalystssuch as dirhenium heptaoxide and rhenium-carbon; a copper chromium oxidecatalyst; a molybdenum oxide catalyst; a vanadium oxide catalyst; and atungsten oxide catalyst. Among these catalysts, the palladium catalystis preferable. In particular, the palladium-carrier catalyst ispreferable. Above all, the palladium-carbon and palladium-alumina aremost preferable.

The amount of the hydrogen moving catalyst to be used is usually in therange of from 0.001 to 1.0 gram atom, preferably from 0.002 to 0.2 gramatom in terms of a metallic atom per gram molecule of the amine.

The method of the present invention is characterized by using asulfur-free polar solvent. Examples of the sulfur-free polar solventinclude N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea,methyl isobutyl ketone, tetrahydrofuran, dioxane,1,3-dimethylimidazolizinone, glymes such as ethylene glycol dimethylether and diethylene glycol dimethyl ether, methyl salicylate, phenoland phenols, for example, alkylphenols such as methylphenol and2,4,6-trimethylphenol as well as alkoxyphenols such as 3-methoxyphenoland 4-methoxyphenol. If necessary, they may be used in combinations oftwo or more thereof. Dimethyl sulfoxide and sulfolane are similarlywithin the category of the polar solvents, but they are not used becausethey contain sulfur which is poisonous to the hydrogen moving catalyst.

The amount of the sulfur-free polar solvent to be used is preferably0.1-6.0 times by weight, more preferably 0.3-3.0 times by weight of thecyclohexanone or the nucleus-substituted cyclohexanone.

It is also within the category of the present invention to use analkaline metal compound and/or an alkaline earth metal compound as acocatalyst. The use of the cocatalyst leads to the effect that the lifeof the hydrogen moving catalyst can be prolonged.

Usable examples of the alkali metal compound and/or the alkaline earthmetal compound which can be added as the cocatalyst are hydroxides,carbonates, bicarbonates and the like of alkali metals and alkalineearth metals. Typical examples of these compounds include lithiumhydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide,magnesium hydroxide, sodium carbonate, potassium carbonate and sodiumhydrogen carbonate. Above all, sodium hydroxide and potassium hydroxideare preferable. These cocatalysts may be used singly or in combinationsof two or more thereof. The cocatalyst does not have to be added to thereaction system separately from the above-mentioned dehydrogenationcatalyst. For example, after a noble metal supporting catalyst has beenprepared, a salt, a hydroxide or the like of an alkali metal and/or analkaline earth metal may be additionally supported as the alkali metalcomponent and/or the alkaline earth metal component on the noble metalsupporting catalyst, and the thus formed catalyst may be used.

The amount of the cocatalyst to be used is preferably in the range offrom 2 to 30% by weight, more preferably from 5 to 20% by weight, interms of the alkali metal and/or the alkaline earth metal, based on theweight of the catalyst metal.

It is also a preferable embodiment of the present invention to add, tothe reaction using the above-mentioned cocatalyst, an organic acid inwhich a logarithm (pKa) of a reciprocal of an acid dissociation constantis in the range of from 3.5 to 6.0.

The preferable pKa of the organic acid is in the range of from 4.0 to5.0. If the pKa of the organic acid is less than this range, the Schiffbase is unstable, and if it is more than the above-mentioned range, thedehydrogenation reaction is impaired. Examples of the organic acidinclude acetic acid, propionic acid, butyric acid, isobutyric acid,valerianic acid, isovalerianic acid, hexanic acid, cyclohexanecarboxylicacid, octanoic acid, crotonic acid, vinylacetic acid, benzoic acid,anisic acid, cinnamic acid, phenylacetic acid and 2-naphthoic acid. Theamount of the organic acid to be used is preferably in the range of from50 to 2000% by weight, more preferably from 70 to 800% by weight basedon the weight of the catalyst metal.

In the case that the nitro compound is used as the hydrogen acceptor inthe presence of the catalyst of a noble metal in the group VIII and thesulfur-free solvent to produce the amine and the cyclohexanone or thenucleus-substituted cyclohexanone is simultaneously reacted with theamine to prepare the aromatic secondary amino compound, the usedcatalyst can be recovered and then reused. In this case, if the alkalimetal compound and/or the alkaline earth metal compound as thecocatalyst and the organic acid having a pKa of 3.5 to 6.0 are added tothe reaction system, the amount of the catalyst to be added in eachoperation can be decreased as much as possible, and a reaction rate anda yield can be maintained.

It is advantageous that the reaction is carried out under the removal ofwater, and thus a technique is suitable in which water is removed fromthe reaction mixture while azeotropic distillation is done by the use ofa solvent such as benzene, toluene or xylene.

The temperature at the reaction is usually in the range of from 120° to250° C., preferably from 140° to 200° C.

In the above-mentioned reaction, when the raw materials are placed in areactor, it is a preferable manner that the (co)catalyst, the solventand the amine are previously put in the reactor, stirred and thenheated, and the (nucleus-substituted) cyclohexanone and the nitrocompound are then simultaneously dropped into the reactor to carry outthe above-mentioned reaction. Needless to say, the (nucleus-substituted)cyclohexanone and the nitro compound are first mixed and then added tothe reaction.

The mixture obtained by the above-mentioned reaction is treated in anordinary manner such as distillation, crystallization or extraction. Forexample, the solution in which the reaction has already been brought toan end is filtered to separate the catalyst therefrom. The thusrecovered catalyst can be reused. The resultant filtrate can beconcentrated to recover the solvent. The produced aromatic secondaryamino compound in the reactor can be directly used without anytreatment, but if necessary, it may be purified by distillation,crystallization or the like.

In accordance with the further aspect of the invention whereinaminodiphenylamine (hereinafter abbreviated as "ADPA") is prepared byreacting phenylenediamine (hereinafter abbreviated as "PD") withcyclohexanone in the presence of a hydrogen transfer catalyst in asulfur-free polar solvent while using nitroaniline (hereinafterabbreviated as "NA") as a hydrogen acceptor, it is important to use asulfur-free polar solvent. Examples of the sulfur-free polar solventinclude N,N-dimethylformamide, N,N-dimethylacetamide; tetramethylurea;methyl isobutyl ketone, tetrahydrofuran, dioxane and1,3-dimethylimidazolidinone; glymes such as ethylene glycol dimethylether, diethylene glycol dimethyl ether and triethylene glycol dimethylether; and phenols such as methyl salicylate, phenol, alkylphenols suchas methylphenol and 2,4,6-trimethylphenol, and alkoxyphenols such as3-methoxyphenol and 4-methoxyphenol. These solvents can be used eithersingly or in combination.

Incidentally, sulfur-containing polar solvents such as dimethylsulfoxideand sulfolane exhibit poisonous action against hydrogen transfercatalysts and are hence not preferred.

Any known hydrogen transfer (moving) catalysts can be used in theprocess of the present invention. Specific examples include thosementioned above including nickel/carrier catalysts such as those formedby having Raney nickel, reduced nickel or nickel borne on variouscarriers such as diatomaceous earth, alumina, pumice, silica gel andacid clay; cobalt catalysts such as Raney cobalt, reduced cobalt, cobaltand cobalt/carrier catalysts; palladium catalysts such as palladiumblack, palladium oxide, colloidal palladium, palladium/carbon,palladium/barium sulfate and palladium/barium carbonate; platinumcatalysts such as platinum black, colloidal platinum, platinized sponge,platinum oxide, platinum sulfide and platinum/carbon; rhodium catalystssuch as colloidal rhodium, rhodium/carbon and rhodium oxide; platinumgroup catalysts such as ruthenium catalysts; rhenium catalysts such asdirhenium heptaoxide and rhenium/carbon; copper chromate catalysts;molybdenum oxide catalysts; vanadium oxide catalysts; and tungsten oxidecatalysts. Among these catalysts, it is preferred to use a palladiumcatalyst. In particular, use of a palladium/carrier catalyst, notably apalladium/carbon or palladium/alumina is preferred. These hydrogentransfer catalysts can be used generally in a proportion of 0.001-1.0gram atom, preferably 0.002-0.2 gram atom in terms of metal atoms pergram molecule of cyclohexanone.

According to the method of the further aspect of the present invention,a Schiff base is formed by condensation of PD and cyclohexanone,followed by the formation of ADPA through dehydrogenation. During themethod, NA is used as a receptor for resulting hydrogen. In this manner,NA is converted to PD in the reaction system and by the reaction of thePD and the other raw material, that is, cyclohexanone, ADPA is formedfurther.

At this time, it is possible to convert 0.67 mole of NA to PD per moleof the Schiff base. For the full and effective utilization of hydrogenoccurring in the reaction system, it is therefore sufficient if themolar ratio of NA to cyclohexanone is set at 0.67. Abundance of NA atthis stage tends to result in a lower reaction velocity and is hence notbeneficial. An unduly small molar ratio of PD/cyclohexanone, on theother hand, tends to cause further reaction of ADPA, which has beenformed in the reaction system, with cyclohexanone so thatN,N'-diphenylphenylene-diamine (hereinafter abbreviated as "N,N'-DPPA")would be by-produced. To avoid these drawbacks, it is preferred to add0.67 mole of NA and at least 0.33 mole of PD per mole of cyclohexanonefrom the beginning of the reaction and then to react them. It is morepreferred to conduct the reaction with the sum of NA and PD beingmaintained at 1.4 moles or more, especially 1.7 mole or more per mole ofcyclohexanone.

In the method of this aspect of the present invention, all the rawmaterials can be charged together at once in a reaction vessel at thebeginning of the reaction. It is however important to conduct thereaction while simultaneously adding cyclohexanone and NA dropwise intoa liquid mixture of the hydrogen transfer catalyst, PD and thesulfur-free polar solvent. Needless to say, they can be mixed first andthen added dropwise. This makes it possible to always maintain thePD/cyclohexanone molar ratio at a still higher level in the reactionsystem, thereby allowing the target product to be obtained in a highyield.

The reaction can also be conducted while separating water from thereaction mixture by azeotropically distilling it off together with asolvent such as benzene, toluene or xylene.

The reaction temperature can be selected generally from a range of140°-250° C., preferably from a range of 160°-200° C.

The ADPA so formed can be obtained by processing the reaction mixture ina manner known per se in the art, such as distillation, crystallizationor extraction, after the completion of the reaction. For example, thereaction mixture is filtered subsequent to the completion of thereaction, whereby the catalyst is separated. The catalyst so recoveredcan be reused. The filtrate is concentrated to recover the solvent. TheADPA left in the reaction vessel can be used, as is, as a raw materialfor the next reaction in some instances but, if necessary, is purifiedby distillation, crystallization or the like.

According to the present invention, the desired aromatic secondary aminocompound can be obtained under extremely moderate conditions and in ahigh yield.

Now, the various aspects of the present invention will be described indetail in reference to examples.

EXAMPLE A1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 1.6 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 10 g ofdiethylene glycol dimethyl ether, 17.33 g (0.1 mol) of N-cyclohexylideneaniline and 8.29 g (0.067 mol) of nitrobenzene. Afterward, the reactorwas heated up to 160° C. with stirring, and reaction was then carriedout for 4 hours by maintaining the reactor at 158°-162° C. During thisreaction, water present in the catalyst and water produced by thereaction were removed from the reaction system by adding benzene to thereactor to cause azeotropy, condensing water by the reflux condenser,and then separating it by the separator. The amount of the removed waterwas 1.8 g. Next, the reaction solution was cooled to room temperature,and the 5% Pd/C was then removed from the reaction solution byfiltration. The resultant filtrate was analyzed by the use of gaschromatography. The conversion of an imine was 100%, and the yield ofdiphenylamine was 87.6%.

EXAMPLES A2 TO A8

Reactions were carried out by the same procedure as in Example A1 exceptthat diethylene glycol dimethyl ether in Example A1 was replaced withvarious polar solvents shown in Table 1.

The results are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                                              Conversion                                                                              Yield of                                                            of Imine  Diphenylamine                                 Example                                                                              Solvent        (mol %)   (mol %)                                       ______________________________________                                        A2     N,N-           100.0     89.5                                                 dimethylacetamide                                                      A3     N,N'-dimethylimida-                                                                          100.0     88.2                                                 zolidinone                                                             A4     p-cresol       99.3      84.1                                          A5     N,N-           100.0     87.7                                                 dimethylformamide                                                      A6     Tetramethylurea                                                                              99.5      87.0                                          A7     N-methylpyrrolidone                                                                          98.9      83.8                                          A8     Methyl salicylate                                                                            99.8      86.5                                          ______________________________________                                    

EXAMPLE A9

Reaction was carried out by the same procedure as in Example A1 exceptthat in place of nitrobenzene in Example A1, 23.87 g (0.202 mol) ofa-methylstyrene were used as a hydrogen acceptor. As a result, theconversion of an imine was 100%, and the yield of diphenylamine was85.9%.

COMPARATIVE EXAMPLE A1

Reaction was carried out by the same procedure as in Example A1 exceptthat diethylene glycol dimethyl ether was not used. As a result, theconversion of an imine was 96.1%, and the yield of diphenylamine was72.3%.

COMPARATIVE EXAMPLE A2

Reaction was carried out by the same procedure as in Example A1 exceptthat in place of diethylene glycol dimethyl ether in Example A1,p-tert-butyltoluene was used as a solvent. As a result, the conversionof an imine was 94.0%, and the yield of diphenylamine was 72.6%.

EXAMPLE B1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 2.57 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 22.23 g ofN,N-dimethylformamide, 20-51 g (0.1 mol) ofN-(4-methylcyclohexylidene)-4-methylaniline and 9.24 g (0.067 mol) ofp-nitrotoluene. Afterward, the reactor was heated up to 140° C. withstirring, and reaction was then carried out for 4 hours by maintainingthe reactor at 138°-142° C. During this reaction, water present in thecatalyst and water produced by the reaction were removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 2.9 g. Next, the reactionsolution was cooled to room temperature, and the 5% Pd/C was thenremoved from the reaction solution by filtration. The resultant filtratewas analyzed by the use of gas chromatography. The conversion of animine was 100%, and the yield of 4,4'-dimethyldiphenylamine was 85.3%.

EXAMPLES B2 TO B6

Reactions were carried out by the same procedure as in Example B1 exceptthat N,N-dimethylformamide in Example B1 was replaced with various polarsolvents shown in Table 2 and reaction temperature was set to 160° C.

The results are set forth in Table 2.

                  TABLE 2                                                         ______________________________________                                                             Conversion                                                                              Yield of                                                            of Imine  Diphenylamine                                  Example Solvent      (mol %)   (mol %)                                        ______________________________________                                        B2      N,N'-        99.4      94.9                                                   dimethylimida-                                                                zolidinine                                                            B3      p-cresol     99.6      91.4                                           B4      Phenol       99.5      88.3                                           B5      Diethylene glycol                                                                          99.5      91.1                                                   dimethyl ether                                                        B6      p-methoxyphenol                                                                            99.8      93.4                                           ______________________________________                                    

EXAMPLES B7 TO B14

Reactions were carried out by the same procedure as in Example B1 exceptthat in place of the combination ofN-(4-methylcyclohexylidene)-4-methylaniline and p-nitrotoluene inExample B1, combinations of various N-cyclohexylidene amino compoundsand hydrogen acceptors shown in Table 3 were used.

The results are set forth in Table 3.

                  TABLE 3                                                         ______________________________________                                                                        Con-                                                                          version                                       Ex-   N-Cyclohexylidene-                                                                            Hydrogen  (mol  Yield                                   ample amino Compound  Acceptor  %)    (mol %)                                 ______________________________________                                        B7    N-(4-methylcyclohexyl-                                                                        o-nitro-  96.2  90.8                                          idene)-2-methylaniline                                                                        toluene                                                 B8    N-(3-ethylcyclohexyl-                                                                         p-nitro-  99.1  94.2                                          idene)-4-methylaniline                                                                        toluene                                                 B9    N-(2-methylcyclohexyl-                                                                        p-nitro-  100.0 96.1                                          idene)-4-methylaniline                                                                        toluene                                                 B10   N-cyclohexylidene-                                                                            m-nitro-  98.9  92.1                                          3-ethylaniline  toluene                                                 B11   N-(4-methylcyclohexyl-                                                                        4-nitro-  99.2  93.1                                          idene)-4-methoxyaniline                                                                       anisole                                                 B12   N-(4-methylcyclohexyl-                                                                        4-nitro-  99.3  93.2                                          idene)-4-phenoxyaniline                                                                       diphenyl-                                                                     ether                                                   B13   N-(4-methoxycyclo-                                                                            4-fluoro- 92.3  89.1                                          hexylidene)-4-fluoro-                                                                         nitro-                                                        aniline         benzene                                                 B14   N-(4-methylcyclohexyl-                                                                        4-nitro-  95.6  91.1                                          idene)-4-hydroxyaniline                                                                       phenol                                                  ______________________________________                                    

EXAMPLE B15

Reaction was carried out by the same procedure as in Example B1 exceptthat in place of p-nitrotoluene in Example B1, 23.87 g (0.202 mol) ofα-methylstyrene were used as a hydrogen acceptor. As a result, theconversion of an imine was 89.1%, and the yield of4,4'-dimethyldiphenylamine was 82.1%.

COMPARATIVE EXAMPLE B1

Reaction was carried out by the same procedure as in Example B1 exceptthat N,N-dimethylformamide was not used. As a result, the conversion ofan imine was 51.9%, and the yield of 4,4'-dimethyldiphenylamine was37.4%.

COMPARATIVE EXAMPLE B2

Reaction was carried out by the same procedure as in Example B1 exceptthat in place of N,N-dimethylformamide in Example B1,p-tert-butyltoluene was used as a solvent. As a result, the conversionof an imine was 49.1%, and the yield of 4,4'-dimethyldiphenylamine was35.3%.

COMPARATIVE EXAMPLE B3

Reaction was carried out by the same procedure as in Example B7 exceptthat N,N-dimethylformamide was not used. As a result, the conversion ofan imine was 31.3%, and the yield of 4,2'-dimethyldiphenylamine was15.5%.

COMPARATIVE EXAMPLE B4

Reaction was carried out by the same procedure as in Example B9 exceptthat N,N-dimethylformamide was not used. As a result, the conversion ofan imine was 12.1%, and the yield of 2,4'-dimethyldiphenylamine was4.3%.

EXAMPLE C1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed3.72 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co., Ltd.and 20 g of diethylene glycol dimethyl ether, and in the drop-pingdevice was prepared a mixed solution of 34.66 g (0.2 mol) ofN-cyclohexylidene aniline and 16.58 g (0.13 mol) of nitrobenzene.Afterward, the reactor was heated up to 160° C. with stirring, and afterthe removal of water present in the catalyst, the solution in thedropping device was dropped over 4 hours, while a temperature of158°-162° C. was maintained. After completion of the dropping, thesolution was stirred for 0.5 hour, while this temperature range wasmaintained. Water produced during this step was removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 4.8 g. Next, the reactionsolution in the reactor was cooled to room temperature, and the 5% Pd/Cwas then removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof an imine was 100%, and the yield of diphenylamine was 98.5%.

EXAMPLES C2 TO C8

Reactions were carried out by the same procedure as in Example C1 exceptthat diethylene glycol dimethyl ether in Example C1 was replaced withvarious polar solvents shown in Table 4.

The results are set forth in Table 4.

COMPARATIVE EXAMPLE C1

Reaction was carried out by the same procedure as in Example C1 exceptthat in place of diethylene glycol dimethyl ether in Example C1,p-tert-butyltoluene was used as a solvent. As a result, the conversionof an imine was 35.0%, and the selectivity of diphenylamine was 90.2%.

                  TABLE 4                                                         ______________________________________                                                              Conversion                                                                              Yield of                                                            of Imine  Diphenylamine                                 Example                                                                              Solvent        (mol %)   (mol %)                                       ______________________________________                                        C2     Diethylene glycol                                                                            100.0     98.4                                                 diethyl ether                                                          C3     N,N'-dimethylimida-                                                                          100.0     98.5                                                 zolidinone                                                             C4     N,N-           100.0     98.7                                                 dimethylformamide                                                      C5     N,N-           100.0     99.0                                                 dimethylacetamide                                                      C6     Tetramethylurea                                                                              99.0      97.0                                          C7     N-methylpyrrolidone                                                                          91.0      89.3                                          C8     Methyl salicylate                                                                            97.0      95.0                                          C9     p-cresol       98.0      96.5                                          ______________________________________                                    

EXAMPLE D1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 2.57 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd. and 22.23 g ofN,N-dimethylformamide, and in the dropping device was prepared andstored a mixed solution of 20.51 g (0.1 mol) ofN-(4-methylcyclohexylidene)-4-methylaniline and 9.24 g (0.067 mol) ofp-nitrotoluene. Afterward, the reactor was heated up to 140° C. withstirring, and after the removal of water present in the catalyst, thesolution in the dropping device was dropped over 4 hours, while atemperature of 138°-142° C. was maintained. After completion of thedropping, the solution was stirred for 1 hour, while this temperaturerange was maintained. Water produced during this step was removed fromthe reaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 4.0 g. Next, the reactionsolution was cooled to room temperature, and the 5% Pd/C was thenremoved from the reaction solution by filtration. The resultant filtratewas analyzed by the use of gas chromatography. The conversion of animine was 98.6%, and the yield of 4,4'-dimethyldiphenylamine was 93.5%.

EXAMPLES D2 TO D6

Reactions were carried out by the same procedure as in Example D1 exceptthat N,N-dimethylformamide in Example D1 was replaced with various polarsolvents shown in Table 5 and reaction temperature was set to 160° C.

The results are set forth in Table 5.

                  TABLE 5                                                         ______________________________________                                                              Conversion                                                                              Yield of                                                            of Imine  Ditolylamine                                  Example                                                                              Solvent        (mol %)   (mol %)                                       ______________________________________                                        D2     N,N'-dimethylimida-                                                                          98.2      96.3                                                 zolidinone                                                             D3     p-cresol       99.1      94.1                                          D4     Phenol         99.0      93.4                                          D5     Diethylene glycol                                                                            98.3      95.2                                                 dimethyl ether                                                         D6     p-methoxyphenol                                                                              99.2      95.3                                          ______________________________________                                    

EXAMPLES D7 TO D14

Reactions were carried out by the same procedure as in Example D1 exceptthat the combination of N-cyclohexylidene amino compound and a hydrogenacceptor in Example D1 was changed to combinations shown in Table 6.

The results are set forth in Table 6.

                  TABLE 6                                                         ______________________________________                                                                        Con-                                                                          version                                       Ex-   N-Cyclohexylidene-                                                                            Hydrogen  (mol  Yield                                   ample amino Compound  Acceptor  %)    (mol %)                                 ______________________________________                                        D7    N-(4-methylcyclohexyl-                                                                        o-nitro-  96.1  94.4                                          idene)-2-methylaniline                                                                        toluene                                                 D8    N-(3-ethylcyclohexyl-                                                                         p-nitro-  98.1  96.5                                          idene)-4-methylaniline                                                                        toluene                                                 D9    N-(2-methylcyclohexyl-                                                                        p-nitro-  99.7  98.5                                          idene)-4-methylaniline                                                                        toluene                                                 D10   N-cyclohexylidene-                                                                            m-nitro-  98.8  95.9                                          3-ethylaniline  toluene                                                 D11   N-(4-methylcyclohexyl-                                                                        4-nitro-  98.1  94.9                                          idene)-4-methoxyaniline                                                                       anisole                                                 D12   N-(4-methylcyclohexyl-                                                                        4-nitro-  98.2  95.3                                          idene)-4-phenoxyaniline                                                                       diphenyl-                                                                     ether                                                   D13   N-(4-methoxycyclo-                                                                            4-fluoro- 90.6  89.1                                          hexylidene)-4-fluoro-                                                                         nitro-                                                        aniline         benzene                                                 D14   N-(4-methylcyclohexyl-                                                                        4-nitro-  96.0  93.7                                          idene)-4-hydroxyaniline                                                                       phenol                                                  ______________________________________                                    

EXAMPLE E1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 1.86 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 0.24 g of1N-NaOH, 10 g of diethylene glycol dimethyl ether, 17.33 g (0.1 mol) ofN-cyclohexylidene aniline and 8.29 g (0.067 mol) of nitrobenzene.Afterward, the reactor was heated up to 160° C. with stirring, andreaction was then carried out for 2 hours by maintaining the reactor at158°-162° C. During this reaction, water present in the catalyst andwater produced by the reaction were removed from the reaction system byadding benzene to the reactor to cause azeotropy, condensing water bythe reflux condenser, and then separating it by the separator. Theamount of the removed water was 2.6 g. Next, the reaction solution wascooled to room temperature, and the 5% Pd/C was then removed from thereaction solution by filtration. The resultant filtrate was analyzed bythe use of gas chromatography. The conversion of an imine was 100%, andthe yield of diphenylamine was 93.0%.

EXAMPLES E2 TO E8 AND COMPARATIVE EXAMPLES E1 TO E3

Reactions were carried out by the same procedure as in Example E1 exceptthat diethylene glycol dimethyl ether in Example E1 was replaced withvarious polar solvents shown in Table 7.

The results are set forth in Table 7.

                  TABLE 7                                                         ______________________________________                                                                       Con-                                                                          version                                                                             Yield                                                                   of    of                                                                      Imine Diphenyl-                                Ex-                   Cocata-  (mol  amine                                    ample Solvent         lyst     %)    (mol %)                                  ______________________________________                                        E2    N,N-dimethylacetamide                                                                         NaOH     100.0 94.2                                     E3    N,N'-           NaOH     100.0 93.5                                           dimethylimidazolidinone                                                 E4    p-cresol        NaOH     98.8  90.4                                     E5    N,N-dimethylformamide                                                                         NaOH     100.0 92.8                                     E6    Tetramethylurea NaOH     99.2  90.6                                     E7    N-methylpyrrolidone                                                                           NaOH     98.4  89.7                                     E8    Methyl salicylate                                                                             NaOH     99.6  92.2                                     Comp. --              NaOH     97.5  84.8                                     Ex. E1                                                                        Comp. --              --       92.5  68.1                                     Ex. E2                                                                        Comp. p-tert-butyltoluene                                                                           NaOH     91.1  67.4                                     Ex. E3                                                                        ______________________________________                                    

EXAMPLES E9 AND E10

Reactions were carried out by the same procedure as in Example E1 exceptthat in place of 0.24 g of 1N-NaOH in Example E1, an alkali metalcompound and/or an alkaline earth metal compound shown in Table 8 wasused as a co-catalyst.

The results are set forth together with those of Example E1 in Table 8.

                  TABLE 8                                                         ______________________________________                                                          Con-                                                        Cocatalyst          version  Yield of                                                           Amount*   of Imine                                                                             Diphenylamine                              Example Kind      (wt %/Pd) (mol %)                                                                              (mol %)                                    ______________________________________                                        E1      NaOH      Na: 11.9  100.0  93.0                                       E9      Ca(OH).sub.2                                                                            Ca: 20    100.0  92.3                                       E10     NaOH +    Na: 5     100.0  93.0                                               Mg(OH).sub.2                                                                            Mg:12                                                       ______________________________________                                         *The amount of the cocatalyst in terms of an alkali metal and/or an           alkaline earth metal.                                                    

EXAMPLE F1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 2.57 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 0.30 g of1N-NaOH, 22.23 g of N,N-dimethylformamide, 20.51 g (0.1 mol) ofN-(4-methylcyclohexylidene)-4-methylaniline and 9.24 g (0.067 mol) ofp-nitrotoluene. Afterward, the reactor was heated up to 140° C. withstirring, and reaction was then carried out for 2 hours by maintainingthe reactor at 138°-142° C. During this reaction, water present in thecatalyst and water produced by the reaction were removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 3.6 g. Next, the reactionsolution was cooled to room temperature, and the 5% Pd/C was thenremoved from the reaction solution by filtration. The resultant filtratewas analyzed by the use of gas chromatography. The conversion of animine was 99.7%, and the yield of 4,4'-dimethyldiphenylamine was 90.9%.

COMPARATIVE EXAMPLE F1

Reaction was carried out by the same procedure as in Example F1 exceptthat N,N-dimethylformamide was not used. As a result, the conversion ofan imine was 46.6%, and the yield of 4,4'-dimethyldiphenylamine was36.0%.

COMPARATIVE EXAMPLE F2

Reaction was carried out by the same procedure as in Example F1 exceptthat 1N-NaOH and N,N-dimethylformamide were not used. As a result, theconversion of an imine was 45.3%, and the yield of4,4'-dimethyldiphenylamine was 31.5%.

EXAMPLES F2 TO F6

Reactions were carried out by the same procedure as in Example F1 exceptthat N,N-dimethylformamide in Example F1 was replaced with various polarsolvents shown in Table 9 and reaction temperature was set to 160° C.

The results are set forth in Table 9.

                  TABLE 9                                                         ______________________________________                                                                         Yield of                                                          Conversion of                                                                             Ditolylamine                                 Example Solvent      Imine (mol %)                                                                             (mol %)                                      ______________________________________                                        F2      N,N'-        98.5        95.2                                                 dimethyl-                                                                     imidazolidinone                                                       F3      p-cresol     100.0       94.6                                         F4      Phenol       99.3        90.6                                         F5      Diethylene glycol                                                             dimethyl ether                                                                             98.7        93.1                                         F6      p-methoxyphenol                                                                            98.8        94.1                                         ______________________________________                                    

EXAMPLES F7 AND F8

Reactions were carried out by the same procedure as in Example F1 exceptthat in place of 0.3 g of 1N-NaOH in Example F1, an alkaline metalcompound and/or an alkaline earth metal compound shown in Table 10 wasused as a co-catalyst.

The results are set forth together with those of Example F1 in Table 10.

                  TABLE 10                                                        ______________________________________                                                          Con-                                                        Cocatalyst          version  Yield of                                                           Amount*   of Imine                                                                             Diphenylamine                              Example Kind      (wt %/Pd) (mol %)                                                                              (mol %)                                    ______________________________________                                        F1      NaOH      Na: 10.7  99.7   90.9                                       F7      Ca(OH).sub.2                                                                            Ca: 20    99.7   89.8                                       F8      NaOH +    Na: 5     100.0  90.6                                               Mg(OH).sub.2                                                                            Mg: 12                                                      ______________________________________                                         *The amount of the cocatalyst in terms of an alkali metal and/or an           alkaline earth metal.                                                    

EXAMPLES F9 TO F16

Reactions were carried out by the same procedure as in Example F1 exceptthat the combination of N-(4-methyl-cyclohexylidene)-4-methylaniline andp-nitrotoluene in Example F1 was changed to combinations ofN-cyclohexylidene amino compounds and hydrogen acceptors shown in Table11.

The results are set forth in Table 11.

                  TABLE 11                                                        ______________________________________                                                                        Con-                                                                          version                                       Ex-   N-Cyclohexylidene-                                                                            Hydrogen  (mol  Yield                                   ample amino Compound  Acceptor  %)    (mol %)                                 ______________________________________                                        F9    N-(4-methylcyclohexyl-                                                                        o-nitro-  97.9  94.0                                          idene)-4-methylaniline                                                                        toluene                                                 F10   N-(3-ethylcyclohexyl-                                                                         p-nitro-  98.3  95.2                                          idene)-4-methylaniline                                                                        toluene                                                 F11   N-(2-methylcyclohexyl-                                                                        p-nitro-  99.8  97.1                                          idene)-4-methylaniline                                                                        toluene                                                 F12   N-cyclohexylidene-                                                                            m-nitro-  99.1  94.7                                          3-ethylaniline  toluene                                                 F13   N-(4-methylcyclohexyl-                                                                        4-nitro-  98.5  93.5                                          idene)-4-methoxy-                                                                             anisole                                                       aniline                                                                 F14   N-(4-methylcyclo-                                                                             4-nitro-  98.5  93.6                                          hexylidene)-4-phenoxy-                                                                        diphenyl                                                      aniline         ether                                                   F15   N-(4-methoxycyclo-                                                                            4-fluoro- 90.8  88.3                                          hexylidene)-4-fluoro-                                                                         nitro-                                                        aniline         benzene                                                 F16   N-(4-methylcyclohexyl-                                                                        4-nitro-  96.2  92.8                                          idene)-4-hydroxyaniline                                                                       phenol                                                  ______________________________________                                    

COMPARATIVE EXAMPLE F3

Reaction was carried out by the same procedure as in Example F9 exceptthat N,N-dimethylformamide in Example F9 was not used. As a result, theconversion of an imine was 55.2%, and the yield of4,2'-dimethyldiphenylamine was 42.3%.

COMPARATIVE EXAMPLE F4

Reaction was carried out by the same procedure as in Example F9 exceptthat 1N-NaOH and N,N-dimethylformamide in Example F9 were not used. As aresult, the conversion of an imine was 17.0%, and the yield of4,2'-dimethyldiphenylamine was 12.5%.

COMPARATIVE EXAMPLE F5

Reaction was carried out by the same procedure as in Example F11 exceptthat N,N-dimethylformamide in Example F11 was not used. As a result, theconversion of an imine was 48.2%, and the yield of2,4'-dimethyldiphenylamine was 35.8%.

COMPARATIVE EXAMPLE F6

Reaction was carried out by the same procedure as in Example F11 exceptthat 1N-NaOH and N,N-dimethylformamide in Example F11 were not used. Asa result, the conversion of an imine was 11.3%, and the yield of2,4'-dimethyldiphenylamine was 3.5%.

EXAMPLE G1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 1.86 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 0.24 g of1N-NaOH, 17.33 g (0.1 mol) of N-cyclohexylideneaniline, 8.29 g (0.067mol) of nitrobenzene. Afterward, the reactor was heated up to 160° C.with stirring, and reaction was then carried out for 3 hours bymaintaining the reactor at 158°-162° C. During this reaction, waterpresent in the catalyst and water produced by the reaction were removedfrom the reaction system by adding benzene to the reactor to causeazeotropy, condensing water by the reflux condenser, and then separatingit by the separator. The amount of the removed water was 2.7 g. Next,the reaction solution was cooled to room temperature, and the 5% Pd/Cwas then removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof an imine was 99.4%, and the yield of diphenylamine was 86.7%.Examples G2 to G10 and Comparative Example G1 Reactions were carried outby the same procedure as in Example G1 except that in place of 0.24 g of1N-NaOH in Example G1, various kinds of cocatalysts were used in variousamounts as shown in Table 12.

The results are set forth together with those of Example G1 in Table 12.

                  TABLE 12                                                        ______________________________________                                                Cocatalyst  Conversion                                                                              Yield of                                                           Amount*  of      Di-                                       Example/           (wt %/   Imine   phenylamine                               Comp. Example                                                                           Kind     Pd)      (mol %) (mol %)                                   ______________________________________                                        Example G1                                                                              NaOH     11.9     99.4    86.7                                      Example G2                                                                              NaOH     20       100.0   87.5                                      Example G3                                                                              Na.sub.2 CO.sub.3                                                                      12       99.8    86.9                                      Example G4                                                                              NaHCO.sub.3                                                                            12       99.0    86.0                                      Example G5                                                                              KOH      6        100.0   87.6                                      Example G6                                                                              LiOH     5        98.5    84.5                                      Example G7                                                                              Ca(OH).sub.2                                                                           20       97.7    83.9                                      Example G8                                                                              Mg(OH).sub.2                                                                           12       98.7    84.8                                      Example G9                                                                              NaOH +   Na: 10   99.2    85.9                                                Ca(OH).sub.2                                                                           Ca: 10                                                     Example G10                                                                             KOH +    K: 5     99.7    86.5                                                Mg(OH).sub.2                                                                           Mg: 12                                                     Comp.     --       --       90.1    69.2                                      Example G1                                                                    ______________________________________                                         *The amount of the cocatalyst in terms of an alkali metal and/or an           alkaline earth metal.                                                    

EXAMPLE H1

In a 100 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 2.57 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 0.30 g of1N-NaOH, 20.51 g (0.1 mol) ofN-(4-methylcyclohexylidene)-4-methylaniline and 9.24 g (0.067 mol) ofp-nitrotoluene. Afterward, the reactor was heated up to 160° C. withstirring, and reaction was the carried out for 3 hours by maintainingthe reactor at 158°-162° C. During this reaction, water present in thecatalyst and water produced by the reaction were removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 3.0 g. Next, the reactionsolution was cooled to room temperature, and the 5% Pd/C was thenremoved from the reaction solution by filtration. The resultant filtratewas analyzed by the use of gas chromatography. The conversion of animine was 98.2%, and the yield of 4,4'-dimethyldiphenylamine was 85.5%.

EXAMPLES H2 TO H6

Reactions were carried out by the same procedure as in Example H1 exceptthat in place of a cocatalyst in Example H1, various kinds ofcocatalysts were used in various amounts as shown in Table 13.

The results are set forth together with those of Example H1 in Table 13.

                  TABLE 13                                                        ______________________________________                                        Cocatalyst          version  Yield of                                                           Amount*   of Imine                                                                             Diphenylamine                              Example Kind      (wt %/Pd) (mol %)                                                                              (mol %)                                    ______________________________________                                        H1      NaOH      10.7      98.2   85.5                                       H2      NaOH      20        98.6   86.7                                       H3      NaOH      5         97.2   83.5                                       H4      NaHCO.sub.3                                                                             12        98.2   85.1                                       H5      Ca(OH).sub.2                                                                            20        96.8   82.8                                       H6      NaOH +    Na: 10    98.7   84.7                                               Ca(OH).sub.2                                                                            Mg: 10                                                      ______________________________________                                         *The amount of the cocatalyst in terms of an alkali metal and/or an           alkaline earth metal.                                                    

EXAMPLES H7 TO H14

Reactions were carried out by the same procedure as in Example H1 exceptthat the combination of an N-cyclohexylidene amino compound and ahydrogen acceptor in Example H1 was changed to combinations shown inTable 14.

The results are set forth in Table 14.

                  TABLE 14                                                        ______________________________________                                                                        Con-                                                                          version                                       Ex-   N-Cyclohexylidene-                                                                            Hydrogen  (mol  Yield                                   ample amino Compound  Acceptor  %)    (mol %)                                 ______________________________________                                        H7    N-(4-methylcyclohexyl-                                                                        o-nitro-  95.2  85.3                                          idine)-2-methylaniline                                                                        toluene                                                 H8    N-(3-ethylcyclohexyl-                                                                         p-nitro-  98.3  88.6                                          idene)-4-methylaniline                                                                        toluene                                                 H9    N-(2-methylcyclo-                                                                             p-nitro-  99.1  90.3                                          hexylidene)-4-methyl-                                                                         toluene                                                       aniline                                                                 H10   N-cyclohexylidene-                                                                            m-nitro-  97.6  86.3                                          3-ethylaniline  toluene                                                 H11   N-(4-methylcyclo-                                                                             4-nitro-  97.9  87.2                                          hexylidene)-4-methoxy-                                                                        anisole                                                       aniline                                                                 H12   N-(4-methylcyclohexyl-                                                                        4-nitro-  98.1  87.0                                          idene)-4-phenoxy-                                                                             diphenyl                                                      aniline         ether                                                   H13   N-(4-methoxycyclo-                                                                            4-fluoro- 89.8  81.9                                          hexylidene)-4-fluoro-                                                                         nitro-                                                        aniline         benzene                                                 H14   N-(4-methylcyclohexyl-                                                                        4-nitro-  91.2  82.6                                          idene)-4-hydroxyaniline                                                                       phenol                                                  ______________________________________                                    

COMPARATIVE EXAMPLE H1

Reaction was carried out by the same procedure as Example H1 except that1N-NaOH was not used. As a result, the conversion of an imine was 79.9%,and the yield of 4,4'-dimethyldiphenylamine was 66.8%.

COMPARATIVE EXAMPLE H2

Reaction was carried out by the same procedure as Example H7 except that1N-NaOH was not used. As a result, the conversion of an imine was 61.3%,and the yield of 4,2'-dimethyldiphenylamine was 35.3%.

COMPARATIVE EXAMPLE H3

Reaction was carried out by the same procedure as Example H9 except that1N-NaOH was not used. As a result, the conversion of an imine was 55.9%,and the yield of 4,2'-dimethyldiphenylamine was 34.1%.

EXAMPLE I1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 5.59 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 25.68 g ofdiethylene glycol dimethyl ether, 13.97 g (0.15 mol) of aniline, 29.44 g(0.3 mol) of cyclohexanone and 24.87 g (0.2 mol) of nitrobenzene.Afterward, the reactor was heated up to 160° C. with stirring, andreaction was then carried out for 3 hours by maintaining the reactor at158°-162° C. Water present in the catalyst and water produced duringthis reaction was removed from the reaction system by adding benzene tothe reactor to cause azeotropy, condensing water by the refluxcondenser, and then separating it by the separator. The amount of theremoved water was 12.4 g. Next, the reaction solution was cooled to roomtemperature, and the 5% Pd/C was then removed from the reaction solutionby filtration. The resultant filtrate was analyzed by the use of gaschromatography. The conversion of cyclohexanone was 100%, and the yieldof diphenylamine was 86.8%.

EXAMPLES I2 TO I8

Reactions were carried out by the same procedure as in Example I1 exceptthat diethylene glycol dimethyl ether in Example I1 was replaced withvarious polar solvents shown in Table 15.

The results are set forth in Table 15.

                  TABLE 15                                                        ______________________________________                                                                         Yield of                                     Exam-                Conversion of                                                                             Diphenylamine                                ple   Solvent        Imine (mol %)                                                                             (mol %)                                      ______________________________________                                        I2    N,N-dimethyl-  100.0       90.2                                               acetamide                                                               I3    N,N'-          98.9        86.2                                               dimethyl-                                                                     imidazolidinone                                                         I4    p-cresol       100.0       91.7                                         I5    N,N-dimethyl-  100.0       91.4                                               formamide                                                               I6    Tetramethylurea                                                                              98.2        87.4                                         I7    N-methylpyrrolidone                                                                          97.4        85.8                                         ______________________________________                                    

COMPARATIVE EXAMPLE I1

Reaction was carried out by the same procedure as in Example I1 exceptthat diethylene glycol dimethyl ether was not used. As a result, theconversion of cyclohexanone was 96.6%, and the yield of diphenylaminewas 76.3%.

COMPARATIVE EXAMPLE I2

Reaction was carried out by the same procedure as in Example I1 exceptthat in place of diethylene glycol dimethyl ether, p-tert-butyltoluenewas used as a solvent. As a result, the conversion of cyclohexanone was91.1%, and the yield of diphenylamine was 67.3%.

EXAMPLE I8

Reaction was carried out by the same procedure as in Example I1 exceptthat 32.39 g (0.39 mol) of cyclohexanone, 9.31 g (0.1 mol) of anilineand 24.62 g (0.2 mol) nitrobenzene were used. As a result, the yield ofdiphenylamine was 89.5%, and 1.8% of triphenylamine and 2.9% ofN-cyclohexylaniline were produced.

EXAMPLE J1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 7.72 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 60.00 g ofN,N-dimethylformamide, 16.07 g (0.15 mol) of p-toluidine, 33.65 g (0.3mol) of 4-methylcyclohexanone and 27.43 g (0.2 mol) of p-nitrotoluene.Afterward, the reactor was heated up to 140° C. with stirring, andreaction was then carried out for 3 hours by maintaining the reactor at134°-142° C. Water present in the catalyst and water produced duringthis reaction were removed from the reaction system by adding benzene tothe reactor to cause azeotropy, condensing water by the refluxcondenser, and then separating it by the separator. The amount of theremoved water was 12.34 g. Next, the reaction solution was cooled toroom temperature, and the 5% Pd/C was then removed from the reactionsolution by filtration. The resultant filtrate was analyzed by the useof gas chromatography. The conversion of 4-methylcyclohexanone was98.6%, and the yield of ditolylamine was 91.6%.

EXAMPLES J2 TO J7

Reactions were carried out by the same procedure as in Example J1 exceptthat N,N-dimethylformamide in Example J1 was replaced with various polarsolvents shown in Table 16 and reaction temperature was set to 160° C.

The results are set forth in Table 16.

                  TABLE 16                                                        ______________________________________                                                                          Yield of                                                            Conversion                                                                              Ditolylamine                                Example                                                                              Solvent          (mol %)   (mol %)                                     ______________________________________                                        J2     N,N-dimethylacetamide                                                                          99.8      90.2                                        J3     N,N'-            98.9      89.2                                               dimethylimidazolidinone                                                J4     p-cresol         100.0     94.3                                        J5     Diethylene glycol                                                                              98.0      89.4                                               dimethyl ether                                                         J6     Tetramethylurea  98.7      87.9                                        J7     N-methylpyrrolidone                                                                            97.4      88.8                                        ______________________________________                                    

COMPARATIVE EXAMPLE J1

Reaction was carried out by the same procedure as in Example J1 exceptthat N,N-dimethylformamide was not used. As a result, the conversion of4-methylcyclohexanone was 51.6%, and the yield of ditolylamine was 7.9%.

COMPARATIVE EXAMPLE J2

Reaction was carried out by the same procedure as in Example J1 exceptthat in place of N,N-dimethylformamide in Example J1, xylene was used asa solvent. As a result, the conversion of p-methylcyclohexanone was53.7%, and the yield of ditolylamine was 9.0%.

EXAMPLES J8 TO J13

Reaction was carried out by the same procedure as in Example J1 exceptthat the combination of p-toluidine, 4-methylcyclohexanone andp-nitrotoluene was replaced with materials shown in Table 17.

The results are set forth in Table 17.

                                      TABLE 17                                    __________________________________________________________________________        Cyclohexanone                                                                 (nucleus-                                        Con-                     Ex- substituted          Nitro-      Desired         version                                                                            Yield               ample                                                                             compound)                                                                              Amine       Compound    Compound        (mol                                                                               (mol                __________________________________________________________________________                                                              %)                  J8                                                                                 ##STR5##                                                                               ##STR6##                                                                                  ##STR7##                                                                                  ##STR8##       97.1 90.7                J9                                                                                 ##STR9##                                                                               ##STR10##                                                                                 ##STR11##                                                                                 ##STR12##      100.0                                                                              89.1                J10                                                                                ##STR13##                                                                              ##STR14##                                                                                 ##STR15##                                                                                 ##STR16##      99.5 87.1                J11                                                                                ##STR17##                                                                              ##STR18##                                                                                 ##STR19##                                                                                 ##STR20##      99.6 90.0                J12                                                                                ##STR21##                                                                              ##STR22##                                                                                 ##STR23##                                                                                 ##STR24##      98.1 89.5                J13                                                                                ##STR25##                                                                              ##STR26##                                                                                 ##STR27##                                                                                 ##STR28##      98.9 88.9                __________________________________________________________________________

EXAMPLE K1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed5.59 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 25.68 g of diethylene glycol dimethyl ether and 13.97 g (0.15 mol)of aniline, and in the dropping device was prepared and stored a mixedsolution of 29.44 g (0.3 mol) of cyclohexanone and 24.87 g (0.2 mol) ofnitrobenzene. Afterward, the reactor was heated up to 160° C. withstirring, and after the removal of water present in the catalyst, thesolution in the dropping device was dropped over 4 hours, while atemperature of 158°-162° C. was maintained. After completion of thedropping, the solution was stirred for 0.5 hour, while this temperaturerange was maintained. Water produced during this step was removed fromthe reaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 12.6 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof cyclohexanone was 100%, and the yield of diphenylamine was 99.2%.

EXAMPLES K2 TO K8

Reactions were carried out by the same procedure as in Example K1 exceptthat diethylene glycol dimethyl ether in Example K1 was replaced withvarious polar solvents shown in Table 18.

The results are set forth in Table 18.

                  TABLE 18                                                        ______________________________________                                                                         Yield of                                     Exam-                  Conversion                                                                              Diphenylamine                                ple   Solvent          (mol %)   (mol %)                                      ______________________________________                                        K2    N,N-dimethylacetamide                                                                          100.0     98.8                                         K3    N,N'-                                                                         dimethylimidazolidinone                                                                        100.0     98.5                                         K4    p-cresol         98.9      97.1                                         K5    N,N-dimethylformamide                                                                          100.0     99.1                                         K6    Tetramethylurea  99.5      98.0                                         K7    N-methylpyrrolidone                                                                            96.8      94.9                                         K8    Methyl salicylate                                                                              98.7      96.8                                         ______________________________________                                    

COMPARATIVE EXAMPLE K1

Reaction was carried out by the same procedure as in Example K1 exceptthat in place of diethylene glycol dimethyl ether in Example K1,p-tert-butyltoluene was used as a solvent. As a result, the conversionof cyclohexanone was 77.5%, and the yield of diphenylamine was 48.5%.

EXAMPLE L1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed7.72 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 60.00 g of N,N-dimethylformamide and 16.07 g (0.15 mol) ofp-toluidine, and in the dropping device was prepared and stored a mixedsolution of 33.65 g (0.3 mol) of 4-methylcyclohexanone and 27.43 g (0.2mol) of p-nitrotoluene. Afterward, the reactor was heated up to 140° C.with stirring, and after the removal of water present in the catalyst,the solution in the dropping device was dropped over 6 hours, while atemperature of 134°-142° C. was maintained. After completion of thedropping, the solution was stirred for 1 hour, while this temperaturerange was kept up. Water produced during this step was removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 12.5 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof 4-methylcyclohexanone was 99.6%, and the yield of ditolylamine was97.7%.

EXAMPLES L2 TO L7

Reactions were carried out by the same procedure as in Example L1 exceptthat N,N-dimethylformamide in Example L1 was replaced with various polarsolvents shown in Table 19 and reaction temperature was set to 160° C.

The results are set forth in Table 19.

                  TABLE 19                                                        ______________________________________                                                                          Yield of                                                            Conversion                                                                              Ditolylamine                                Example                                                                              Solvent          (mol %)   (mol %)                                     ______________________________________                                        L2     N,N-dimethylacetamide                                                                          99.7      97.1                                        L3     N,N'-            99.1      96.5                                               dimethylimidazolidinone                                                L4     p-cresol         99.9      98.1                                        L5     Diethylene glycol                                                                              98.0      96.1                                               dimethyl ether                                                         L6     Tetramethylurea  99.2      97.1                                        L7     N-methylpyrrolidone                                                                            98.7      96.9                                        ______________________________________                                    

EXAMPLES L8 TO L13

Reactions were carried out by the same procedure as in Example L1 exceptthat p-toluidine, 4-methylcyclohexanone and p-nitrotoluene in Example L1were replaced with various materials shown in Table 20.

The results are set forth in Table 20.

                                      TABLE 20                                    __________________________________________________________________________        Cyclohexanone                                                                 (nucleus-                                        Con-                     Ex- substituted          Nitro-      Desired         version                                                                            Yield               ample                                                                             compound)                                                                              Amine       Compound    Compound        (mol                                                                               (mol                __________________________________________________________________________                                                              %)                  L8                                                                                 ##STR29##                                                                              ##STR30##                                                                                 ##STR31##                                                                                 ##STR32##      98.2 95.1                L9                                                                                 ##STR33##                                                                              ##STR34##                                                                                 ##STR35##                                                                                 ##STR36##      99.8 97.8                L10                                                                                ##STR37##                                                                              ##STR38##                                                                                 ##STR39##                                                                                 ##STR40##      99.6 96.8                L11                                                                                ##STR41##                                                                              ##STR42##                                                                                 ##STR43##                                                                                 ##STR44##      99.8 98.8                L12                                                                                ##STR45##                                                                              ##STR46##                                                                                 ##STR47##                                                                                 ##STR48##      98.9 96.7                L13                                                                                ##STR49##                                                                              ##STR50##                                                                                 ##STR51##                                                                                 ##STR52##      99.3 96.9                __________________________________________________________________________

EXAMPLE M1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer and a stirrer were placed 7.72 g of 5% Pd/Ccontaining 50% of water made by N.E. Chemcat Co., Ltd., 0.91 g of1N-NaOH (Na content=10.8 wt %/Pd), 60.00 of N,N-dimethylformamide, 16.07g (0.15 mol) of p-toluidine, 33.65 g (0.3 mol) of 4-methylcyclohexanoneand 27.43 g (0.2 mol) of p-nitrotoluene. Afterward, the reactor washeated up to 140° C. with stirring, and reaction was then carried outfor 3 hours by maintaining the reactor at 138°-142° C. water present inthe catalyst and water produced during this reaction were removed fromthe reaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 15.22 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof 4-methylcyclohexanone was 99.8%, and the yield of ditolylamine was94.2%.

EXAMPLE M2

In a 300 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed4.66 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 1.21 g of 1N-NaOH, 0.33 g of butyric acid, 42.80 g of diethyleneglycol dimethyl ether and 23.28 g (0.25 mol) of aniline, and in thedropping device was prepared and stored a mixed solution of 49.07 g (0.5mol) of cyclohexanone and 41.45 g (0.33 mol) of nitrobenzene. Thereactor was heated to 160° C. with stirring, and after the removal ofwater present in the catalyst, the solution in the dropping device wasdropped over 4 hours, while a temperature of 158°-162° C. wasmaintained. After completion of the dropping, the solution was stirredfor 0.5 hour, while this temperature range was kept up. Water producedduring this step was removed from the reaction system by adding benzeneto the reactor to cause azeotropy, condensing water by the refluxcondenser, and then separating it by the separator. The amount of theremoved water was 21.0 g. Next, the reaction solution was cooled to roomtemperature, and the 5% Pd/C was then removed from the reaction solutionby filtration. The resultant filtrate was analyzed by the use of gaschromatography. The conversion of cyclohexanone was 100%, and the yieldof diphenylamine was 99.9%.

In succession, the previously recovered catalyst was used, and 5% Pd/Ccontaining 50% of water, NAOH and butyric acid were added as shown inTable 21 and reaction was then similarly carried out. As a result, theaverage amount of the added new 5% Pd/C catalyst necessary to maintain areaction rate and a selectivity was about 3% of its initial amount.

                  TABLE 21                                                        ______________________________________                                                Amount of                                                                     Added                      Con-  Selec-                                       New                  Butyric                                                                             version                                                                             tivity                               Number of                                                                             Catalyst   1N-NaOH   Acid  (mol  (mol                                 Recycling                                                                             5% Pd/C (g)                                                                              (g)       (g)   %)    %)                                   ______________________________________                                        1       --         --        0.33  100.0 99.8                                 2       --         --        0.33  100.0 99.7                                 3       --         --        0.33  100.0 99.7                                 4       --         --        0.33  100.0 99.1                                 5       0.70       0.18      0.33  100.0 99.7                                 6       --         --        0.33  99.7  98.6                                 7       0.47       0.12      0.33  100.0 99.5                                 8       --         --        0.33  100.0 99.0                                 9       --         --        0.33  98.7  97.3                                 10      0.23       0.06      0.33  100.0 99.3                                 ______________________________________                                    

EXAMPLE M3

In a 300 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed4.66 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 42.80 g of diethylene glycol dimethyl ether and 23.28 g (0.25 mol)of aniline, and in the dropping device was prepared and stored a mixedsolution of 49.07 g (0.5 mol) of cyclohexanone and 41.45 g (0.33 mol) ofnitrobenzene. Afterward, the reactor was heated up to 160° C. withstirring, and after the removal of water present in the catalyst, thesolution in the dropping device was dropped over 4 hours, while atemperature of 158°-162° C. was maintained. After completion of thedropping, the solution was stirred for 0.5 hour, while this temperaturerange was maintained. Water produced during this step was removed fromthe reaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 21.0 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof cyclohexanone was 100%, and the yield of diphenylamine was 99.2%.

In succession, the previously recovered catalyst was used, and 5% Pd/Cwas added as shown in Table 22 and the reaction was then similarlycarried out. As a result, the average amount of the added new 5% Pd/Ccatalyst necessary to maintain a reaction rate and a selectivity wasabout 15% of its initial amount.

                  TABLE 22                                                        ______________________________________                                                 Amount of Added                                                      Number of                                                                              New 5% Pd/C   Conversion Selectivity                                 Recycling                                                                              Catalyst (g)  (mol %)    (mol %)                                     ______________________________________                                        1        0.47          98.7       96.7                                        2        0.47          94.5       92.4                                        3        0.93          95.7       93.3                                        4        0.93          96.0       93.7                                        5        0.93          96.2       94.0                                        6        0.47          93.6       90.8                                        7        0.70          95.3       92.6                                        8        0.70          94.1       91.7                                        9        0.70          93.4       91.2                                        10       0.70          92.7       90.4                                        ______________________________________                                    

EXAMPLE N1

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed7.72 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 0.91 g of 1N-NaOH, 0.55 g of butyric acid, 60.00 g ofN,N-dimethylformamide and 16.07 g (0.15 mol) of toluidine, and in thedropping device was prepared and stored a mixed solution of 33.65 g (0-3mol) of 4-methylcyclohexanone and 27.43 g (0.2 mol) of p-nitrotoluene.Afterward, the reactor was heated up to 140° C. with stirring, and afterthe removal of water present in the catalyst, the solution in thedropping device was dropped over 6 hours, while a temperature of134°-142° C. was maintained. After completion of the dropping, thesolution was stirred for 1 hour, while this temperature range wasmaintained. Water produced during this step was removed from thereaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 12.6 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof 4-methylcyclohexanone was 99.8%, and the yield of ditolylamine was98.8%.

In succession, the previously recovered catalyst was used, and 5% Pd/Ccontaining 50% of water, NAOH and butyric acid were added as shown inTable 23 and the reaction was then similarly carried out. As a result,the average amount of the added new catalyst necessary to maintain areaction rate and a selectivity was about 6.0% of its initial amount.

                  TABLE 23                                                        ______________________________________                                                Amount of                                                                     Added                      Con-  Selec-                                       New                  Butyric                                                                             version                                                                             tivity                               Number of                                                                             Catalyst   1N-NaOH   Acid  (mol  (mol                                 Recycling                                                                             5% Pd/C (g)                                                                              (g)       (g)   %)    %)                                   ______________________________________                                        1       0.39       0.08      0.55  100.0 99.2                                 2       0.19       0.08      0.55  100.0 99.1                                 3       0.19       0.08      0.55  100.0 99.0                                 4       0.19       0.08      0.55  100.0 99.1                                 5       0.19       0.08      0.55  100.0 98.9                                 ______________________________________                                    

EXAMPLE N2

In a 200 ml round bottom flask equipped with a reflux condenser with aseparator, a thermometer, a dropping device and a stirrer were placed7.72 g of 5% Pd/C containing 50% of water made by N.E. Chemcat Co.,Ltd., 60.00 g of N,N-dimethylformamide and 16.07 g (0.15 mol) oftoluidine, and in the dropping device was prepared and stored a mixedsolution of 33.65 g (0.3 mol) of 4-methylcyclohexanone and 27.43 g (0.2mol) of p-nitrotoluene. Afterward, the reactor was heated up to 140° C.with stirring, and after the removal of water present in the catalyst,the solution in the dropping device was dropped over 6 hours, while atemperature of 134°-142° C. was maintained. After completion of thedropping, the solution was stirred for 1 hour, while this temperaturerange was maintained. Water produced during this step was removed fromthe reaction system by adding benzene to the reactor to cause azeotropy,condensing water by the reflux condenser, and then separating it by theseparator. The amount of the removed water was 12.5 g. Next, thereaction solution was cooled to room temperature, and the 5% Pd/C wasthen removed from the reaction solution by filtration. The resultantfiltrate was analyzed by the use of gas chromatography. The conversionof 4-methylcyclohexanone was 99.6%, and the yield of ditolylamine was98.7%.

In succession, the previously recovered catalyst was used, and the newcatalyst was added as much as an average amount of about 8.3% based onthe initial amount as shown in Table 24 and the reaction was thensimilarly carried out. The results obtained were shown in the sametable.

                  TABLE 24                                                        ______________________________________                                                 Amount of Added                                                      Number of                                                                              New Catalyst  Conversion Selectivity                                 Recycling                                                                              5% Pd/C (g)   (mol %)    (mol %)                                     ______________________________________                                        1        0.39          98.5       96.7                                        2        0.19          95.6       92.8                                        3        0.39          95.8       92.7                                        4        0.39          93.9       89.9                                        5        0.59          95.1       90.5                                        ______________________________________                                    

The method of the further aspect of the present invention willhereinafter be described specifically by the following examples.

EXAMPLE O1

Charged in a 200-ml round bottom flask equipped with a separator-fittedreflux condenser, a thermometer and a stirrer were 3.03 g of 5% Pd/C(water content: 50 wt. %; product of N.E. Chemcat Corp.), 64.0 g ofN,N-dimethylacetamide, 7.21 g (0.07 mole) of paraphenylenediamine(hereinafter abbreviated as "PPD"), 19.63 g (0.20 mole) of cyclohexanone(hereinafter abbreviated as "CH") and 18.42 g (0.13 mole) ofparanitroaniline (hereinafter abbreviated as "PNA"). While maintainingthe internal temperature at 158°-162° C., the contents were continuouslystirred for 5 hours. During that period, benzene was charged so thatresulting water was azeotropically distilled off. The azeotropicallydistilled water-benzene mixture was condensed in the reflux condenserand was then separated through the separator. The reaction mixture wasthen cooled to room temperature and the 5% Pd/C was filtered off fromthe reaction mixture. The filtrate was analyzed by gas chromatography,thereby obtaining the following data:

Conversion of CH: 99.95 (mol % per CH)

Yield of P-ADPA: 49.87 (mol per CH)

By-production of N,N'-p-DPPA: 36.50 (mol % per CH)

Recovery of non-dehydrogenated product: 3.26 (mol % per CH)

EXAMPLES O2-O4

In each example, a reaction was conducted in a similar manner to ExampleO1 except that the amount of PPD in Examples O2-O4 was changed as shownin Table 25. The results are presented in Table 25.

COMPARATIVE EXAMPLE 1

A reaction was conducted in a similar manner to Example O1 except forthe substitution of p-cymene for N,N-dimethylacetamide in Example O1.The results are presented in Table 25.

                                      TABLE 25                                    __________________________________________________________________________            (PPD + PNA)                                                                           Conversion                                                                          Yield of                                                                           By-production                                                                         Recovery of un-                                    /CH (molar                                                                            of CH p-ADPA                                                                             of N,N'-p-                                                                            dehydrogenated                                     ratio)  (mol %)                                                                             (mol %)                                                                            DPPA    product (mol %)                            __________________________________________________________________________    Example O2                                                                            1.4     100   72.57                                                                              14.21   5.14                                       Example O3                                                                            1.7     100   75.18                                                                              10.67   5.53                                       Example O4                                                                            2.0     99.93 79.51                                                                              7.13    5.06                                       Comp. Ex. O1                                                                          1.0     100   28.70                                                                              1.27    45.98                                      __________________________________________________________________________

EXAMPLE O5

Charged in a 200-ml round bottom flask equipped with a separator-fittedreflux condenser, a thermometer, a dropping device and a stirrer were3.03 g of 5% Pd/C (water content: 50 wt. %; product of N.E. ChemcatCorp.), 40.0 g of N,N-dimethylacetamide, and 7.21 g (0.07 mole) of PPD.A mixed solution consisting of 19.63 g (0.20 mole) of CH and 18.42 g(0.13 mole) of PNA was prepared and charged in the dropping device. Theinternal temperature of the flask was raised to 160° C. under stirringand, while maintaining the internal temperature at 158°-162° C., thesolution in the dropping device was added dropwise over 6 hours. Afterthe completion of the dropwise addition, the contents of the flask werestirred for 1 hour while maintaining the internal temperature within theabove temperature range. During that period, benzene was charged so thatresulting water was azeotropically distilled off. The azeotropicallydistilled water-benzene mixture was condensed in the reflux condenserand was then separated through the separator. The reaction mixture wasthen cooled to room temperature and the 5% Pd/C was filtered off fromthe reaction mixture. The filtrate was analyzed by gas chromatography,thereby obtaining the following data:

Conversion of CH: 99.51 (mol % per CH)

Yield of P-ADPA: 54.00 (mol % per CH)

By-production of N,N'-p-DPPA: 35.65 (mol % per CH)

Recovery of non-dehydrogenated product: 9.72 (mol % per CH)

EXAMPLES O6-O7 & COMPARATIVE EXAMPLE O2

In each example, a reaction was conducted in a similar manner to ExampleO5 except that the corresponding polar solvent (Examples O6 and O7) orthe non-polar solvent (Comparative Example O2) shown in Table 26 wasused instead of N,N-dimethylacetamide in Example O5. The results arepresented in Table 26.

                                      TABLE 26                                    __________________________________________________________________________                    Conversion                                                                          Yield of                                                                           By-production                                                                         Recovery of un-                                            of CH p-ADPA                                                                             of N,N'-p-                                                                            dehydrogenated                                     Solvent (mol %)                                                                             (mol %)                                                                            DPPA    product (mol %)                            __________________________________________________________________________    Example O6                                                                            1,3-Dimethyl-                                                                         100   56.56                                                                              29.13   9.49                                               imidazolidinone                                                       Example O7                                                                            Diethylene                                                                            100   57.51                                                                              32.75 4.37                                                 glycol dimethyl                                                               ether                                                                 Comp. Ex. O2                                                                          p-Cymene                                                                              100   32.13                                                                              1.36    48.98                                      __________________________________________________________________________

EXAMPLES O8-O12

In each example, a reaction was conducted in a similar manner to ExampleO5 except that the amount of PPD in Examples O5 was changed to set the(PPD+PNA)/CH ratio at the corresponding value shown in Table 27.

The results are presented in Table 27.

                                      TABLE 27                                    __________________________________________________________________________            (PPD + PNA)                                                                           Conversion                                                                          Yield of                                                                           By-production                                                                         Recovery of un-                                    /CH (molar                                                                            of CH p-ADPA                                                                             of N,N'-p-                                                                            dehydrogenated                                     ratio)  (mol %)                                                                             (mol %)                                                                            DPPA    product (mol %)                            __________________________________________________________________________    Example O8                                                                            1.187   100   75.12                                                                              22.90   2.91                                       Example O9                                                                            1.437   100   81.03                                                                              16.16   2.19                                       Example O10                                                                           1.687   100   86.87                                                                              0.67    1.71                                       Example O11                                                                           1.987   100   89.64                                                                              9.12    1.24                                       Example O12                                                                           6.950   100   92.99                                                                              1.66    5.65                                       __________________________________________________________________________

EXAMPLES O13-O15

In each example, a reaction was conducted in a similar manner to ExampleO5 except that PPD and PNA in Example O5 were replaced bymetaphenylenediamine (hereinafter abbreviated as "MPD") andmetanitroaniline (hereinafter abbreviated as "MNA"), respectively, andthe (MPD+MNA)/CH ratio was set at the corresponding value shown in Table28.

The results are presented in Table 28.

                                      TABLE 28                                    __________________________________________________________________________            (MPD + MNA)                                                                            Conversion                                                                          Yield of                                                                           By-production                                                                         Recovery of un-                                   /CH (molar                                                                             of CH m-ADPA                                                                             of N,N'-p-                                                                            dehydrogenated                                    ratio)   (mol %)                                                                             (mol %)                                                                            DPPA    product (mol %)                           __________________________________________________________________________    Example O13                                                                           1.000    99.9  53.4 43.2    0.9                                       Example O14                                                                           1.417    99.9  75.0 18.5    1.3                                       Example O15                                                                           1.917    100   81.8 12.4    0.7                                       __________________________________________________________________________

EXAMPLE O16

Charged in a 200-ml round bottom flask equipped with a separator-fittedreflux condenser, a thermometer, a dropping device and a stirrer were3.03 g of 5% Pd/C (water content: 50 wt. %; product of N.E. ChemcatCorp.), 40.0 g of triethylene glycol dimethyl ether, and 27.04 g (0.25mole) of orthophenylenediamine. A mixed solution consisting of 19.63 g(0.20 mole) of CH and 18.42 g (0.13 mole) of orthonitroaniline wasprepared and charged in the dropping device. The internal temperature ofthe flask was raised to 170° C. under stirring and, while maintainingthe internal temperature at 170°-173° C., the solution in the droppingdevice was added dropwise over 15 hours. After the completion of thedropwise addition, the contents of the flask were stirred for 2 hourswhile maintaining the internal temperature within the above temperaturerange. During that period, benzene was charged so that resulting waterwas azeotropically distilled off. The azeotropically distilledwater-benzene mixture was condensed in the reflux condenser and was thenseparated through the separator. The reaction mixture was then cooled toroom temperature and the 5% Pd/C was filtered off from the reactionmixture. The filtrate was analyzed by gas chromatography, therebyobtaining the following data:

Conversion of CH: 100 (mol % per CH)

Yield of O-ADPA: 63.8 (mol % per CH)

Recovery of non-dehydrogenated product: 35.8 (mol % per CH)

What is claimed is:
 1. A method for preparing an aromatic secondaryamino compound represented by the formula (2) ##STR53## wherein each Ris a hydrogen atom, alkyl group, alkoxy group, amino group, hydroxylgroup or fluorine; R' is an alkyl group, phenyl group, benzyl group,naphthyl group, furyl group, furfuryl group or cyclohexyl group, and R'may be substituted by an alkyl group, alkoxy group, phenyl group,phenoxy group, cyclohexyl group, amino group, substituted amino group,carboxyl group, hydroxyl group or fluorine; and n is an integer of from0 to 5 which comprises the step of reacting cyclohexanone or anucleus-substituted cyclohexanone represented by the formula (3)##STR54## wherein R is defined above, an amine represented by theformula (4)

    R'--NH.sub.2                                               ( 4)

wherein R' is defined above, and a nitro compound as a hydrogen acceptorcorresponding to the amine and represented by the formula (5)

    R'--NO.sub.2                                               ( 5)

wherein R' is defined above in a sulfur-free polar solvent at atemperature in the range of from 120° to 250° C. in the presence of acatalyst selected from the noble metals of Group VIII of the PeriodicTable.
 2. The method for preparing an aromatic secondary amino compoundaccording to claim 1 wherein said reaction is carried out by droppingcyclohexanone or the nucleus-substituted cyclohexanone and the nitrocompound into the sulfur-free polar solvent in which the hydrogen movingcatalyst is dispersed.
 3. The method for preparing an aromatic secondaryamino compound according to claim 1 wherein said reaction is carried outby adding an alkaline metal compound and/or an alkaline earth metalcompound as a cocatalyst.
 4. The method for preparing an aromaticsecondary amino compound according to claim 3 wherein said reaction iscarried out by dropping cyclohexanone or the nucleus-substitutedcyclohexanone and the nitro compound into a mixture obtained by addingthe cocatalyst and the hydrogen moving catalyst to the sulfur-free polarsolvent.
 5. The method for preparing an aromatic secondary aminocompound according to claim 3 wherein an organic acid having a logarithm(pKa) of a reciprocal of an acid dissociation constant in the range offrom 3.5 to 6.0 is further added.
 6. The method for preparing anaromatic secondary amino compound according to claim 4 wherein anorganic acid having a logarithm (pKa) of a reciprocal of an aciddissociation constant in the range of from 3.5 to 6.0 is further addedto the sulfur-free polar solvent.
 7. A process for the preparation ofaminodiphenylamine, which comprises reacting phenylenediamine andcyclohexanone in the presence of a hydrogen transfer catalyst in asulfur-free polar solvent while using nitroaniline as a hydrogenacceptor.
 8. A process according to claim 7, wherein the reaction isconducted while adding nitroaniline and cyclohexanone dropwise into aliquid mixture of the hydrogen transfer catalyst, phenylenediamine andthe sulfur-free polar solvent.